Open Access
Open Peer Review

This article has Open Peer Review reports available.

How does Open Peer Review work?

Towards comprehensive and transparent reporting: context-specific additions to the ICF taxonomy for medical evaluations of work capacity involving claimants with chronic widespread pain and low back pain

  • Urban Schwegler1, 2Email author,
  • Jessica Anner3,
  • Andrea Glässel1,
  • Mirjam Brach1,
  • Wout De Boer3,
  • Alarcos Cieza4 and
  • Bruno Trezzini1
BMC Health Services Research201414:361

DOI: 10.1186/1472-6963-14-361

Received: 18 November 2013

Accepted: 20 August 2014

Published: 29 August 2014

Abstract

Background

Medical evaluations of work capacity provide key information for decisions on a claimant’s eligibility for disability benefits. In recent years, the evaluations have been increasingly criticized for low transparency and poor standardization. The International Classification of Functioning, Disability and Health (ICF) provides a comprehensive spectrum of categories for reporting functioning and its determinants in terms of impairments and contextual factors and could facilitate transparent and standardized documentation of medical evaluations of work capacity. However, the comprehensiveness of the ICF taxonomy in this particular context has not been empirically examined. In this study, we wanted to identify potential context-specific additions to the ICF for its application in medical evaluations of work capacity involving chronic widespread pain (CWP) and low back pain (LBP).

Methods

A retrospective content analysis of Swiss medical reports was conducted by using the ICF for data coding. Concepts not appropriately classifiable with ICF categories were labeled as specification categories (i.e. context-specific additions) and were assigned to predefined specification areas (i.e. precision, coverage, personal factors, and broad concepts). Relevant specification categories for medical evaluations of work capacity involving CWP and LBP were determined by calculating their relative frequency across reports and setting a relevance threshold.

Results

Forty-three specification categories for CWP and fifty-two for LBP reports passed the threshold. In both groups of reports, precision was the most frequent specification area, followed by personal factors.

Conclusions

The ICF taxonomy represents a universally applicable standard for reporting health and functioning information. However, when applying the ICF for comprehensive and transparent reporting in medical evaluations of work capacity involving CWP and LBP context-specific additions are needed. This is particularly true for the documentation of specific pain-related issues, work activities and personal factors. To ensure the practicability of the multidisciplinary evaluation process, the large number of ICF categories and context-specific additions necessary for comprehensive documentation could be specifically allocated to the disciplines in charge of their assessment.

Keywords

International Classification of Functioning Disability and Health (ICF) Medical evaluation of work capacity Disability evaluation Chronic widespread pain Low back pain Context-specific additions

Background

Medical evaluations of work capacity (MEWC) determine a claimant’s diagnoses and work capacity as the key information for decisions on eligibility for benefits provided by national disability insurances. To ensure a fair eligibility decision process, MEWC should be documented as transparently and comprehensibly as possible [1]. Moreover, MEWC should also be comparable in terms of interrater reliability between the medical experts who are in charge of the assessments [2, 3].

In reality, however, MEWC are often reported in a poorly standardized way [2] and charged with low interrater reliability [4]. Furthermore, in many European countries the determination of a health condition is required as a key criterion for disability benefits eligibility [5], Annex] although health conditions taken by themselves are usually only loosely correlated with work ability limitations [6]. In contrast, modern medical thinking defines disability not simply as the consequence of a health condition but as the result of various biopsychosocial interactions [7]. Hence, transparent MEWC require comprehensive reporting of functional limitations and their determinants, not only in terms of impairments or health conditions but also in terms of contextual factors.

The International Classification of Functioning, Disability and Health (ICF) [7] provides a comprehensive biopsychosocial framework that conceptualizes functioning as the interplay between a health condition, body functions and body structures, activities and participation as well as contextual factors, i.e. environmental and personal factors (see Figure 1). The ICF framework thus appears promising for ensuring transparent reporting in MEWC. The ICF taxonomy is considered the worldwide standard for reporting on functioning and disability and offers a comprehensive spectrum of categories for documenting all components of the framework except personal factors which are not classified. In addressing 362 categories on the second level (e.g. b280 Sensation of pain) and up to 1,424 categories on the more specific third or fourth levels (e.g. b2801 Pain in body part and b28013 Pain in back), the ICF taxonomy provides a common language for standardizing MEWC and enhancing their interrater reliability [8].
https://static-content.springer.com/image/art%3A10.1186%2F1472-6963-14-361/MediaObjects/12913_2013_Article_3460_Fig1_HTML.jpg
Figure 1

The comprehensive biopsychosocial framework of the ICF. Note: Drawn from [7].

Applying the ICF could be particularly beneficial in MEWC of claimants with chronic pain which are in Switzerland often conducted in multidisciplinary settings. The impact of pain on functioning, and thus on work ability, depends on complex biopsychosocial interactions [9]. Therefore, a comprehensive and accurate documentation of functional limitations and their determinants is needed for transparent MEWC involving chronic pain.

So far, no empirical studies have examined the comprehensiveness of the ICF taxonomy in covering the core content of MEWC. Conceptual papers on the applicability of the ICF in MEWC argue that the ICF is neither useful for describing (in)consistencies and causal relationships between impairments, contextual influences, activity limitations and work ability restrictions, nor for addressing the dynamic development of disability over time [10, 11]. However, since these issues reflect procedural and decisional challenges in MEWC rather than specific aspects related to functioning, they fall beyond the scope of the ICF taxonomy and will not be further dwelled upon in this study.

Yet, the comprehensiveness of the ICF taxonomy in addressing core aspects of specific contexts of application has been empirically studied in fields other than MEWC, including work and pain assessments. A need for context-specific additions to the ICF was identified with regard to the following four areas.

(1) Precision refers to the number of distinct levels of specification within an ICF category [12]. Some categories may not be specific enough for contexts requiring highly accurate reporting of health-related aspects [13]. Existing ICF categories do not allow for describing the pain location or features of pain quality such as pressure, stabbing or rest pain at a sufficient level of detail [14, 15]. Additionally, specific work activities such as “overhead working” or “forward bending stand” cannot be adequately reported with ICF categories [16]. Therefore, when applying the ICF taxonomy for accurate reporting in a specific context, category specifications may be developed for exclusive use in this particular context.

To exploit the maximum precision of the ICF categories for documentation in specific contexts, scholars have advocated using the more accurate third or fourth category levels. For pain assessments, this was mainly motivated by the need to differentiate between specific pain locations [15]. In the work context, the third and fourth category levels allow for distinguishing specific work activities such as sitting or standing [17].

(2) Coverage reflects the ability of the ICF taxonomy to comprehensively capture the spectrum of functioning aspects and environmental factors and has formerly been described with the terms exhaustiveness or width [12]. Some work-related aspects such as “overloading” or “overstressing” can, for instance, not be addressed with ICF categories [18]. To address this issue, items that allow for reporting important context-specific aspects not covered by the ICF could be exclusively generated for a particular context.

(3) Personal factors are currently not classified by the ICF taxonomy, although several studies pointed out the need for standardized personal factor categories [1921]. Psychological aspects that are relevant in the field of chronic pain such as coping strategies, fear-avoidance beliefs or catastrophizing cannot be reported with ICF categories [22, 23]. In the contexts of work and MEWC, it would be important to have categories for the documentation of personal factors such as a claimant’s occupational background, work motivation or expectations regarding return to work [24, 25].

(4) Broad concepts such as quality of life or general health were also mentioned as not being classified by the ICF [26]. However, as the ICF taxonomy aims at categorizing specific aspects related to functioning and health rather than overall concepts, this issue appears to be less pertinent.

Applying the ICF taxonomy to code the content of medical reports is one possible way to empirically test its comprehensiveness in the context of MEWC, and to establish aspects that are not addressable with ICF categories at all or not in a sufficiently specific manner. This is, however, based on the assumption that current medical reports do indeed include the crucial aspects of MEWC. In a recent study [27], we found that the ICF Core Sets for chronic widespread pain (CWP) [23], low back pain (LBP) [28] and two major co-morbidities, i.e. depression [29] and obesity [30], cover the relevant aspects of functioning and environmental factors in reports on Swiss disability claimants with CWP and LBP to a fair extent. However, the study only focused on second level ICF categories. Moreover, a number of concepts in the reports were not appropriately classifiable with the ICF. A more in-depth analysis of these concepts is necessary to properly establish aspects to be added when applying the ICF taxonomy for comprehensive reporting in MEWC.

The present study aims at providing additions to the ICF exclusively for its application in MEWC involving chronic pain and not for an update of the ICF taxonomy in general. Therefore, a context-specific addition (or a specification category) refers to a complement to the ICF taxonomy for this particular field of application. The four abovementioned specification areas (i.e. precision, coverage, personal factors, broad concepts) will serve as a structuring device for presenting the study results.

Objective

The objective of this study was to identify potential context-specific additions to the ICF taxonomy for its application in MEWC involving CWP and LBP.

Specific aims

The specific aims were (1) to identify and specify content of medical reports on claimants with CWP and/or LBP not appropriately classifiable with the ICF; and (2) to determine specification categories as well as third and fourth level ICF categories that appear relevant across these reports.

Methods

Study design

We conducted a retrospective qualitative and quantitative content analysis of 72 medical reports [31]. In the qualitative part the reports were coded using the ICF, while in the quantitative part a frequency analysis of the coded categories was carried out.

Ethics

The study was approved by the Ethics Commission of Basel, Switzerland, project number 134/08, and performed in accordance to the Declaration of Helsinki.

Sample

The available sample included all 209 reports in German that were submitted to the Swiss national disability insurance scheme between February 1st and April 30th 2008, and contained a diagnosis of CWP and/or LBP. We used a selection of International Classification of Diseases (ICD-10) codes as inclusion criteria (see Table 1). The reports were selected and anonymized by insurance employees and could include one, two or more medical disciplines.
Table 1

ICD-10 diagnoses included in the sample

ICD-10 diagnoses for CWP

ICD-10 diagnoses for LBP

F45.0 Somatization disorder

M42 Spinal osteochondrosis (.15-.17, .95-.97)

F45.1 Undifferentiated somatoform disorder

M45 Ankylosing spondylitis

F45.4 Persistent somatoform disorder

M46 Other inflammatory spondylopathies (.0, .1, .2, .3)

F54 Psychological and behavioral factors associated with disorders or diseases classified elsewhere

M47 Spondylosis and (osteo-)arthrosis of spine (.05-.07, .15-.17, .25-.27)

F62.8 Chronic pain personality syndrome

M48 Other spondylopathies (.05-.07, .15-.17, .25-.27)

F32 Mild, moderate and severe depressive episode, with somatic symptoms

M51 Other intervertebral disc disorders (.0, .1)

F33 Recurrent depressive disorder, with somatic symptoms

M53 Other dorsopathies, not elsewhere classified (.25-.27, .3, .86-.87, .96-.97)

F34.1 Dysthymia (in relation with pain)

M54 Dorsalgias (.05-.07, .15-.17, .3, .4, .5, .85-.87)

F43.2 Adjustment disorders

M99 Biomechanical lesions, not elsewhere classified (.03, .13, .23, .33, .43, .53, .63, .73, .83, .93)

M79.7 Fibromyalgia

R52.2 Other chronic pain

R52.9 Pain, unspecified

 

Note: Drawn from [27].

From this available sample we drew a subsample whose final size was determined based on two criteria: (1) saturation, i.e. the assumption that the collected information is sufficient when no new second level ICF category appears in five successive reports analyzed [32, 33]; and (2) heterogeneity, i.e. the proportional inclusion of both the relevant medical disciplines of pain assessment (e.g. rheumatology, psychiatry or neurology) and the index conditions (i.e. CWP, LBP) involved in the reports. The heterogeneity criterion was applied to capture the diversity of the concepts relevant in the present context. Taking into account the two abovementioned heterogeneity dimensions a minimum subsample size of 72 reports, representing about one third of the available sample of 209 reports, was determined. The reports were randomly drawn from the available sample and the order in which they were analyzed was randomly determined.

Analysis

We subdivided the sample into reports with CWP and with LBP diagnoses. Reports including both diagnoses were analyzed twice, once with the pure CWP and once with the pure LBP reports.

Content analysis

In Switzerland, MEWC are usually documented in free text by medical experts. Reports consist of three main sections that comprehensively address the claimant’s situation. (1) The socio-medical history describes the claimant’s occupational, biographical and medical background and his or her functioning in everyday life, including subjective claims regarding impairments and functional limitations. (2) The medical examination aims at an objective assessment of functional capacity and documents the expert’s findings regarding the claimant’s physical or mental impairments leading to the final diagnoses. (3) The work capacity evaluation provides a synthesis of the two previous sections and an appraisal of the claimant’s work capacity based on his or her functional capacity and diagnoses. In addition, the consistency between subjective claims and objective findings is discussed. Finally, a long-term prognosis is provided and measures to improve the claimant’s work capacity are suggested.

We coded the content of the reports using the ICF and established linking rules [34, 35]. Pre-existing medical records on the claimant were not analyzed. First, we divided the reports into units of meaning referring to passages with a common theme (e.g. “the claimant suffers from pain while sitting”). Then, we determined the different concepts underlying a unit of meaning (e.g. pain, sitting) and coded them to the most precise ICF category (e.g. b280 Sensation of pain, d4153 Maintaining a sitting position). To ensure data quality, all reports were coded by two health professionals familiar with the ICF and trained in the linking method. In case of discrepancies, the coders discussed and agreed on their final coding. Any disagreement was resolved by consulting a third subject-matter specialist. Interrater reliability between the two coders was determined based on percentage agreement [36].

The coders also assessed whether concepts reflected limitations or barriers for the claimant (e.g. “the cold weather worsens the claimant’s health”), were facilitators (e.g. “the warm weather supports the claimant’s recovery”), no problem (e.g. “the weather does not influence the claimant’s health”), or facts (e.g. “the weather is usually mild where the claimant lives”).

Concepts not appropriately classifiable with the ICF were labeled with a specification code as either personal factors, not covered, not definable (broad concepts) or health condition. The codes other specified, not definable (within ICF components) or combination category were applied when concepts could not be addressed sufficiently precisely within ICF categories. Table 2 provides examples and definitions for the different types of specification categories.
Table 2

Specification areas, type of specification categories, examples for specification codes and definitions for the different types of specification categories referring to concepts in the medical reports not appropriately codeable with the ICF

Specification area

Type of specification categories and examples for specification codes

Definition of specification category

(1) Precision

Combination category

Location of a body function

 e.g. b7101(s7201)

 e.g. mobility of shoulder joint

Not definable (within ICF components)

Concepts which can be coded to more than one ICF category within a component

 e.g. nd-d(ohw)

 e.g. overhead working

Other specified

Concepts not differentiable within an ICF category

 e.g. d4158

 e.g. maintaining a bending position

(2) Coverage

Not covered

Not covered by the ICF

 e.g. nc-acc

 e.g. accidents

Not covered – work (in)capacity

Not covered within the ICF (general work (in)capacity)

 e.g. nc-WC; nc-WIC

 e.g. work (in)capacity

Health condition

Health conditions

 e.g. hc

 e.g. depression

(3) Personal factors

Personal factors

Personal factors

 e.g. pf-edu

 e.g. educational background

(4) Broad concepts

Not definable (broad concepts)

Not definable broad concepts

 e.g. nd-gh

 e.g. general health

We assigned the categories to the four specification areas precision, coverage, personal factors and broad concepts (see Table 2). Information referring to causal relationships, consistency or time-related aspects was not considered for the content analysis.

Relevance analysis

The relevance analysis only included specification categories and third or fourth level ICF categories assessed as limitations, barriers or facilitators and thus assumed to influence the claimant’s functioning. We removed second level ICF categories identified in our previous study [27] from the analysis. In addition, we excluded concepts from the specification area coverage referring to health condition or to the legal term work (in)capacity and broad concepts. The former because a health condition such as depression can be classified using an ICD-10 code. The latter two since classifying overall concepts would not match the ICF’s basic tenet and is not further increasing a comprehensive and accurate reporting of functioning aspects and their determinants in MEWC.

We operationalized the relevance of a category as its relative frequency across reports, i.e. the percentage of reports it was addressed in at least once, and applied a relevance threshold at 25%. All categories above this threshold were considered relevant context-specific additions to the ICF for MEWC involving CWP and LBP. The selection of a particular threshold always involves an arbitrary element. For the purpose of this study, we first analyzed the frequency and diversity of the categories with regard to three different thresholds, i.e. 75%, 50% and 25%. We eventually settled on the most lenient threshold at 25% so as to arrive at a comprehensive picture of the relevant context-specific additions across reports.Figure 2 illustrates the content selection process applied in our study.
https://static-content.springer.com/image/art%3A10.1186%2F1472-6963-14-361/MediaObjects/12913_2013_Article_3460_Fig2_HTML.jpg
Figure 2

Overview of the content selection process. Notes: * = Second level ICF categories already identified in a previous study [27]; hc = health condition; nd = not definable with the ICF; nc = not covered by the ICF; WC = work capacity; WIC = work incapacity. Boxes shaded in grey refer to concepts that were excluded in the content selection process.

Results

Sample characteristics

The saturation criterion was reached after coding 30 medical reports. However, to fulfill the heterogeneity requirement, we set the minimum size of the subsample to be 72 reports, representing about one third of the available sample of 209 reports. We considered this sample size big enough to ensure a proportional inclusion of the index conditions and the medical disciplines involved in the reports. 27 of the reports contained only a CWP diagnosis, 22 only a LBP diagnosis, and 23 both a CWP and LBP diagnosis. In the CWP group 20 reports included one, 4 two and 26 more than two medical disciplines, while in the LBP group 14 reports consisted of one, 5 of two and 26 of more than two disciplines. In both group of reports, psychiatry and rheumatology were the most frequent medical disciplines.

Interrater reliability

The percentage agreement between the two coders was 78.7% for the ICF categories and 78.8% for the specification categories in the reports.

Reports with CWP diagnoses

Content analysis

A total of 21,562 units of meaning led to 45,365 (100%) codings. Out of these, 24,396 (53.7%) represented pure ICF categories. The rest (20,969 or 46.3%) was not classifiable appropriately or precisely enough with the ICF. Table 3 displays the codings’ frequencies for the different types of specification categories and specification areas.
Table 3

Absolute and relative frequency of the codings for the different types of specification categories and specification areas in relation to the total number of codings (k = 45,365) in the CWP reports (n = 50)

Specification area

Type of specification categories

Absolute frequency

Relative frequency %

(1) Precision

Combination categories

4,775

10.5

Not definable (within components)

592

1.3

Other specified

871

1.9

6,238

13.8

(2) Coverage

Not covered

3,324

7.3

Not covered - work (in)capacity

770

1.7

Health condition

2,243

4.9

6,337

13.9

(3) Personal factors

Personal factors

4,276

9.4

(4) Broad concepts

Not definable (broad concepts)

4,118

9.1

Of the 24,396 (100%) codings referring to ICF categories, 8,413 (34.5%) were coded on the second, 13,810 (56.6%) on the third and 2,173 (8.9%) on the fourth level.

Relevant specification categories

Overall, 5,146 codings for specification categories and 5,482 for third and fourth level ICF categories were assessed as limitations, barriers or facilitators and thus included in the relevance analysis. 454 different specification categories were identified. Forty-three of them passed the 25%-threshold and were considered relevant for medical reports on claimants with CWP. Thirty-one categories belonged to the area precision, 10 to personal factors and 2 to coverage (see Table 4). In addition, 70 third or fourth level ICF categories passed the relevance threshold (see Table 5).
Table 4

Relative frequency of the specification categories (subdivided in specification areas) in the CWP reports (n = 50)

Specification area

Code

Specification category

Relative frequency %

(1) Precision

nd-d(hph-l)

Heavy physical labor

60

b28016(s76002)

Pain in joints (Lumbar vertebral column)

56

b7101(s76002)

Mobility of several joints (Lumbar vertebral column)

56

b2801(s7601)

Pain in body part (Muscles of trunk)

54

b2801(s740)

Pain in body part (Structure of pelvic region)

48

b2801(s720)

Pain in body part (Structure of shoulder region)

46

b28016(s76000)

Pain in joints (Cervical vertebral column)

46

b7101(s76000)

Mobility of several joints (Cervical vertebral column)

46

b2801(s710)

Pain in body part (Structure of head and neck region)

44

b28015(s7500)

Pain in lower limb (Structure of thigh)

44

b1268

Temperament and personality functions, other specified (Aggravation, simulation)

44

b2702(s730)

Sensitivity to pressure (Structure of upper extremity)

42

b28016(s75011)

Pain in joints (Knee joint)

42

b2803(s750)

Radiating pain in a dermatome (Structure of lower extremity)

42

b7350(s75002)

Tone of isolated muscles and muscle groups (Muscles of thigh)

42

b2702(s750)

Sensitivity to pressure (Structure of lower extremity)

38

b28016(s7201)

Pain in joints (Joints of shoulder region)

38

d2408

Handling stress and other psychological demands, other specified (Behavior during medical examination)

38

s76082

Structure of trunk, other specified (Lumbar intervertebral disk)

38

b7350(s7601)

Tone of isolated muscles and muscle groups (Muscles of trunk)

36

nd-d(ohw)

Overhead working

34

nd-d(fp)

Forced postures

34

b28015(s7501)

Pain in lower limb (Structure of lower leg)

32

b28014(s7302)

Pain in upper limb (Structure of hand)

30

b28016(s76001)

Pain in joints (Thoracic vertebral column)

30

b2803(s7500)

Radiating pain in a dermatome (Structure of thigh)

30

b7101(s75001)

Mobility of several joints (Hip joint)

28

b7101(s7401)

Mobility of several joints (Joints of pelvic region)

26

b7101(s76001)

Mobility of several joints (Thoracic vertebral column)

26

nd-d(rep)

Repetitive work activities

26

e1108

Products or substances for personal consumption, other specified (Stimulants like alcohol or nicotine)

26

(2) Coverage

nc-fam

Genetic aspects

70

nc-acc

Accidents

58

(3) Personal factors

pf-othchar

Other personal characteristics (e.g. personal expectations, beliefs and attitudes)

90

pf-exp

Past and current experience (past life events and concurrent events)

88

pf-edu

Education

84

pf-fam

Family and marital status

84

pf-psychassets

Individual psychological assets

76

pf-copstyles

Coping styles

70

pf-lifestyle

Lifestyle

62

pf-socbac

Social background

58

pf-char

Overall behavior pattern and character style

52

 

pf-prof

Profession

52

Table 5

Relative frequency of the third and fourth level ICF categories in the CWP reports (n = 50)

ICF code

Third or fourth level ICF category

Relative frequency %

e5800

Health services

88

b28013

Pain in back

86

b28016

Pain in joints

84

e1101

Drugs

82

b1265

Optimism

78

b28015

Pain in lower limb

76

b28010

Pain in head and neck

76

b1602

Content of thought

74

b7101

Mobility of several joints

74

b2702

Sensitivity to pressure

70

b2803

Radiating pain in a dermatome

70

s7600

Structure of vertebral column

70

d5702

Maintaining one's health

70

b1342

Maintenance of sleep

68

e1650

Financial assets

68

d8700

Personal economic resources

64

b1301

Motivation

60

b1603

Control of thought

60

d4153

Maintaining a sitting position

60

b28014

Pain in upper limb

58

b7350

Tone of isolated muscles and muscle groups

58

s76002

Lumbar vertebral column

58

b2802

Pain in multiple body parts

56

b4552

Fatiguability

56

b1521

Regulation of emotion

54

b1303

Craving

52

s7502

Structure of ankle and foot

48

b1261

Agreeableness

48

d4300

Lifting

48

e5702

Social security policies

48

b1302

Appetite

46

d4150

Maintaining a lying position

46

d7701

Spousal relationships

46

s76001

Thoracic vertebral column

46

d8450

Seeking employment

44

d2402

Handling crisis

44

e5700

Social security services

44

d2303

Managing one's own activity level

42

b2703

Sensitivity to noxious stimulus

40

b2800

Generalized pain

40

b1470

Psychomotor functions

40

d4154

Maintaining a standing position

40

d8502

Full-time employment

38

b1520

Appropriateness of emotion

38

d7601

Child–parent relationships

38

d7602

Sibling relationships

38

b7301

Power of muscles of one limb

36

d8501

Part-time employment

36

b28012

Pain in stomach or abdomen

36

b4200

Increased blood pressure

36

d4501

Walking long distances

36

b7300

Power of isolated muscles and muscle groups

34

b1522

Range of emotion

34

b7305

Power of muscles of the trunk

34

d2401

Handling stress

34

d7600

Parent–child relationships

34

s76003

Sacral vertebral column

34

s7501

Structure of lower leg

32

e2450

Day/night cycles

32

s76000

Cervical vertebral column

32

b1263

Psychic stability

30

b1341

Onset of sleep

30

b7355

Tone of muscles of trunk

30

d4104

Standing

30

d4751

Driving

30

e2250

Temperature

30

b1260

Extraversion

26

b1266

Confidence

26

d5701

Managing diet and fitness

26

d7202

Regulating behaviors within interactions

26

Reports with LBP diagnoses

Content analysis

A total of 21,707 units of meaning resulted in 42,116 (100%) codings. Out of these, 22,333 (53%) represented pure ICF categories. The remainder (19,783 or 47%) was not classifiable appropriately or precisely enough with the ICF. Table 6 presents the codings’ frequencies for the different types of specification categories and specification areas.
Table 6

Absolute and relative frequency of the codings for the different types of specification categories and specification areas in relation to the total number of codings (k = 42,116) in the LBP reports (n = 45)

Specification area

Type of specification categories

Absolute frequency

Relative frequency %

(1) Precision

Combination categories

5,297

12,6

Not definable (within components)

623

1.5

Other specified

1,246

3.0

7,166

17.0

(2) Coverage

Not covered

2,568

6.1

Not covered – work (in) capacity

754

1.8

Health condition

2,571

6.1

5,893

14.0

(3) Personal factors

Personal factors

3,111

7.4

(4) Broad concepts

Not definable (broad concepts)

3,613

8.6

Of the 22,333 (100%) codings referring to ICF categories, 6,712 (30.1%) were coded on the second, 12,588 (56.4%) on the third and 3,033 (13.6%) on the fourth level.

Relevant specification categories

Overall, 4,860 codings for specification categories and 5,184 for third and fourth level ICF categories were assessed as limitations, barriers or facilitators and thus included in the relevance analysis. 438 different specification categories were identified. Fifty-two of them passed the 25%-threshold and were considered relevant for medical reports on claimants with LBP. Forty categories belonged to the area precision, 10 to personal factors and 2 to coverage (see Table 7). In addition, 67 third or fourth level ICF categories passed the relevance threshold (see Table 8).
Table 7

Relative frequency of the specification categories (subdivided in specification areas) in the LBP reports (n = 45)

Specification area

Code

Specification category

Relative frequency %

(1) Precision

b7101(s76002)

Mobility of several joints (Lumbar vertebral column)

84

b28016(s76002)

Pain in joints (Lumbar vertebral column)

80

s76082

Structure of trunk, other specified (lumbar intervertebral disks)

76

b7101(s76002)

Mobility of several joints (Lumbar vertebral column)

69

b2803(s750)

Radiating pain in a dermatome (Structure of lower extremity)

64

nd-d(hph-l)

Heavy physical labor

64

b7350(s75002)

Tone of isolated muscles and muscle groups (Muscles of thigh)

58

b2801(s7601)

Pain in body part (Muscles of trunk)

56

b28016(s7201)

Pain in joints (Joints of shoulder region)

51

b7350(s7601)

Tone of isolated muscles and muscle groups (Muscles of trunk)

49

b2803(s7500)

Radiating pain in a dermatome (Structure of thigh)

47

s76083

Structure of trunk, other specified (sacral intervertebral disks)

47

b7101(s7401)

Mobility of several joints (Joints of pelvic region)

42

nd-d(fp)

Forced postures

42

b7101(s76001)

Mobility of several joints (Thoracic vertebral column)

40

nd-d(ohw)

Overhead working

40

b7101(s75001)

Mobility of several joints (Hip joint)

36

b7101(s7600)

Mobility of several joints (Structure of vertebral column)

36

b1268

Temperament and personality functions, other specified (Aggravation, simulation)

36

d2408

Handling stress and other psychological demands, other specified (Behavior during examination)

36

d4158

Maintaining a body position, other specified (Maintaining a bending position)

36

b28016(s76001)

Pain in joints (Thoracic vertebral column)

33

b2803(s710)

Radiating pain in a dermatome (Structure of head and neck region)

33

b2803(s7502)

Radiating pain in a dermatome (Structure of ankle and foot)

33

b7108

Mobility of joint functions, other specified (Single multiple joint)

33

d4108

Changing a basic body position, other specified (Back or head rotations)

33

b28016(s75011)

Pain in joints (Knee joint)

31

s76080

Structure of trunk, other specified (Cervical intervertebral disks)

31

b2702(s7302)

Sensitivity to pressure (Structure of hand)

29

b2702(s750)

Sensitivity to pressure (Structure of lower extremity)

29

b2801(s7104)

Pain in body part (Muscles of head and neck region)

29

b2801(s720)

Pain in body part (Structure of shoulder region)

29

b750(s75012)

Motor reflex functions (Muscles of lower leg)

29

b2702(s730)

Sensitivity to pressure (Structure of upper extremity)

27

b28014(s7302)

Pain in upper limb (Structure of hand)

27

b28016(s75001)

Pain in joints (Hip joint)

27

b2803(s730)

Radiating pain in a dermatome (Structure of upper extremity)

27

b7301(s750)

Power of muscles of one limb (Structure of lower extremity)

27

nd-d(rep)

Repetitive work activities

27

nd-d(altact)

Alternating work activities

27

(2) Coverage

nc-fam

Genetic aspects

56

nc-acc

Accidents

51

(3) Personal factors

pf-fam

Family and marital status

73

pf-exp

Past and current experience (Past life events and concurrent events)

69

pf-psychassets

Individual psychological assets

67

pf-othchar

Other personal characteristics (e.g. personal expectations, beliefs and attitudes)

62

pf-copstyles

Coping styles

56

pf-edu

Education

56

pf-prof

Profession

47

pf-lifestyle

Lifestyle

44

pf-char

Overall behavior pattern and character style

36

 

pf-socbac

Social background

36

Table 8

Relative frequency of the third and fourth level ICF categories in the LBP reports (n = 45)

ICF code

Third or fourth level ICF category

Relative frequency %

b28013

Pain in back

100

b28016

Pain in joints

98

b7101

Mobility of several joints

98

s7600

Structure of vertebral column

98

s76002

Lumbar vertebral column

93

b2803

Radiating pain in a dermatome

89

d4153

Maintaining a sitting position

89

b7350

Tone of isolated muscles and muscle groups

82

b28010

Pain in head and neck

78

s76001

Thoracic vertebral column

78

e1101

Drugs

76

b28015

Pain in lower limb

76

e5800

Health services

76

b2702

Sensitivity to pressure

71

d4300

Lifting

71

d4154

Maintaining a standing position

64

e1650

Financial assets

62

d8700

Personal economic resources

58

b1342

Maintenance of sleep

58

d4150

Maintaining a lying position

58

b1265

Optimism

56

b4200

Increased blood pressure

56

s76000

Cervical vertebral column

53

s76003

Sacral vertebral column

53

d5702

Maintaining one's health

53

e5702

Social security policies

53

b28014

Pain in upper limb

51

b1602

Content of thought

49

b1303

Craving

47

s7502

Structure of ankle and foot

47

b7301

Power of muscles of one limb

47

d8450

Seeking employment

47

b1301

Motivation

44

d8501

Part-time employment

44

d4105

Bending

44

s7501

Structure of lower leg

42

b4552

Fatiguability

42

b2802

Pain in multiple body parts

42

b7305

Power of muscles of the trunk

42

b1603

Control of thought

40

b1521

Regulation of emotion

40

d4104

Standing

40

d4501

Walking long distances

40

b1261

Agreeableness

38

d8502

Full-time employment

38

e5700

Social security services

38

b1302

Appetite

38

e2450

Day/night cycles

36

d4551

Climbing

36

b1470

Psychomotor control

33

b7300

Power of isolated muscles and muscle groups

33

b28012

Pain in stomach or abdomen

33

b7355

Tone of muscles of trunk

33

s1201

Spinal nerves

31

d2303

Managing one's own activity level

31

b2703

Sensitivity to a noxious stimulus

31

d7701

Spousal relationships

31

b1341

Onset of sleep

31

d7602

Sibling relationships

31

d7601

Child–parent relationships

31

s75011

Knee joint

29

e2250

Temperature

29

b7303

Power of muscles in lower half of the body

29

b7100

Mobility of a single joint

27

s75021

Ankle joint and joints of foot and toes

27

d2401

Handling stress

27

d5701

Managing diet and fitness

27

d2402

Handling crisis

27

Discussion

We identified several potential context-specific additions to the ICF taxonomy for its application in MEWC involving CWP and LBP. Moreover, we found a substantial number of third and fourth level ICF categories to be relevant for this particular context. The specification categories were assigned to the four specification areas precision, coverage, personal factors and broad concepts. For reasons given in the methods section, the categories referring to broad concepts were not considered relevant context-specific additions for the use of the ICF in MEWC.

Precision was in both groups of reports the most common specification area and reflects category specifications that need to be considered when applying the ICF for comprehensive reporting in MEWC involving CWP and LBP. For instance, the ICF category for joint pain (i.e. b28016 Pain in joints) lacks granularity in MEWC as it does not distinguish between different locations of joint pain. Such a differentiation, however, is important in MEWC as joint pain may affect different work activities depending on its location. While pain in the lumbar vertebral column, for example, may limit bending, shoulder pain interferes with activities requiring hand and arm use. Category specifications for different locations of joint pain could facilitate an accurate reporting of such relations when using the ICF in MEWC. In addition, important work activities such as overhead working involve aspects covered by several different ICF categories and cannot be adequately reported with one single ICF category. This problem could be resolved by introducing context-specific additions to the ICF addressing the work activities concerned.

The large number of third or fourth level ICF categories above the relevance threshold indicates their importance when applying the ICF in MEWC involving chronic pain. This is particularly true for describing pain locations on the one hand and work activities on the other, and is consistent with findings of studies in the contexts of work and pain assessments [15, 16].

As to a potential lack of specificity of ICF categories, it needs to be emphasized that the ICF taxonomy aims at providing a universally applicable standard for reporting health and functioning information rather than at offering accurate categories for reporting specific aspects of particular disciplines, contexts or health conditions. In this respect, our findings regarding a lack of specificity of some ICF categories are not surprising, but with regard to the potential applicability of the ICF in the present context nevertheless noteworthy. Alternative to the use of context-specific additions it is also possible to report aspects that cannot be accurately classified with ICF categories by using free text and without applying specific ICF-related codes.

Personal factors are the second important area for context-specific additions to the ICF in MEWC involving CWP and LBP. Standardized reporting of psychological aspects such as coping strategies or pain beliefs [23] as well as occupational experiences or work motivation [24] is crucial for pain and work ability assessments. In MEWC, personal factor categories may be helpful in illustrating whether functional limitations are likely due to a health condition (e.g. “depressive symptoms”) or due to individual characteristics (e.g. “reduced work motivation”). Whilst in the former case claimants may be entitled to receive a disability pension, in the latter they are more likely to be assigned to a return to work program. Most relevant personal factors in the context of MEWC involving chronic pain were found to be the claimant’s educational, occupational and biographical background, behavior patterns as well as personal emotions and cognitions such as, for instance, expectations related to the job [25]. As an alternative to the determination of context-specific additions for personal factors, already existing personal factor taxonomies could be used for standardized reporting such as the one of Geyh et al. [37] or Grotkamp et al. [38]. These taxonomies have recently been applied for coding the content of MEWC involving CWP [25].

In both groups of reports only two categories from the area coverage passed the relevance threshold (i.e. genetic aspects and accidents). This is a good sign regarding the comprehensiveness and exhaustiveness of the ICF in covering the content of MEWC involving chronic pain, and an indicator that adding context-specific aspects not covered by the ICF is a less pressing issue.

Study limitations

Our study has some limitations. First, our sample only includes reports in German from the Swiss national disability insurance. Results are thus not generalizable to other insurance schemes nor to countries with different disability evaluation procedures. To test the generalizability of our findings in other insurance schemes or in other national contexts, further validation studies would be required.

Second, in our study we considered medical reports as the gold standard and benchmark for the comprehensiveness of the ICF in capturing the core content of MEWC. However, it is possible that these reports do not address all aspects that are relevant for MEWC in a sufficiently comprehensive manner. Moreover, it is unknown to what extent the information in these reports addresses the subjective experience of the claimants in an unfiltered, uninterpreted and truly person-centered manner. With the application of a rather lenient relevance threshold at 25%, we increased the probability of capturing a comprehensive picture of the relevant aspects across reports and, thus, alleviated the former of these two limitations. However, additional data sources such as interviews with experts or claimants should be considered to validate our findings.

Practical implications

The context-specific additions to the ICF and the third or fourth level ICF categories we established as relevant for MEWC involving CWP and LBP complete the set of second level categories suggested in our previous study [27]. Our findings are exclusively geared toward the application of the ICF in MEWC involving CWP or LBP and do not represent suggestions for a general adjustment of the ICF taxonomy or for its use in other contexts. Comprehensive documentation based on the ICF categories and the context-specific additions identified in our studies could ensure transparent MEWC and standardize them in terms of what to measure. However, the ICF does not currently provide a proper operationalization for its categories. Therefore, the issue of how to measure the identified categories should be addressed for the time being by assigning validated measurement tools to the categories.

It is obvious that comprehensive reporting involves a considerable amount of categories, which threatens to undermine the practicability of MEWC. In Switzerland, MEWC of claimants with CWP are usually conducted in multidisciplinary settings. To ensure feasible evaluations, the categories could be grouped and assigned to the particular discipline in charge of their assessment (e.g. b152 Emotional functions should be exclusively assessed by psychiatrists). This limits the amount of categories to be assessed by each medical expert and ensures an overall documentation structure of the multidisciplinary evaluations.

Conclusions

The ICF taxonomy represents a universally applicable standard for reporting health and functioning information. However, when applying the ICF for comprehensive and transparent reporting in MEWC involving CWP and LBP context-specific additions are needed. This is particularly true for the documentation of specific pain-related issues, work activities and personal factors. To ensure the practicability of the multidisciplinary evaluation process, the large number of ICF categories and context-specific additions necessary for comprehensive documentation could be specifically allocated to the disciplines in charge of their assessment.

Abbreviations

MEWC: 

Medical evaluations of work capacity

ICF: 

International Classification of Functioning, Disability and Health

CWP: 

Chronic widespread pain

LBP: 

Low back pain

ICD: 

International Classification of Diseases.

Declarations

Acknowledgments

We thank Heinrich Gall and Wolfgang Segerer for their support in preparing the database for the linking process, and Katharina Karl for her support in linking the information of the medical reports to the ICF. We thank Christine Boldt for her guidance in the planning, coordination and preparation of the study.

Authors’ Affiliations

(1)
Swiss Paraplegic Research (SPF)
(2)
Department of Health Sciences and Health Policy, University of Lucerne and SPF
(3)
asim, Academy of Swiss Insurance Medicine, University Hospital Basel
(4)
Faculty of Social and Human Sciences, School of Psychology, University of Southampton

References

  1. Meershoek A, Krumeich A, Vos R: Judging without criteria? Sickness certification in Dutch disability schemes. Sociol Health Illn. 2007, 29 (4): 497-514. 10.1111/j.1467-9566.2007.01009.x.View ArticlePubMedGoogle Scholar
  2. Matheson LN, Kane M, Rodbard D: Development of new methods to determine work disability in the United States. J Occup Rehabil. 2001, 11 (3): 143-154. 10.1023/A:1013070326696.View ArticlePubMedGoogle Scholar
  3. Innes E, Straker L: Attributes of excellence in work-related assessments. Work. 2003, 20 (1): 63-76.PubMedGoogle Scholar
  4. Rudbeck M, Fonager K: Agreement between medical expert assessments in social medicine. Scand J Public Health. 2011, 39 (7): 766-772. 10.1177/1403494811418282.View ArticlePubMedGoogle Scholar
  5. APPLICA, CESEP, European Centre: Study of compilation of disability statistical data from the administrative registers of the member states. 2007, Brussels, Belgium: APPLICA, CESEP and European CentreGoogle Scholar
  6. Loeser JD, Sullivan M: Doctors, diagnosis, and disability: a disastrous diversion. Clin Orthop Relat Res. 1997, 336 (336): 61-66.View ArticlePubMedGoogle Scholar
  7. World Health Organization: International Classification of Functioning, Disability and Health (ICF). 2001, Geneva: World Health OrganizationGoogle Scholar
  8. Kirschneck M, Winkelmann A, Kirchberger I, Glässel A, Ewert T, Stucki G, Cieza A: Anwendung der ICF Core Sets in der Begutachtung von Patienten mit lumbalen Rückenschmerzen und generalisiertem Schmerzsyndrom. Gesundheitswesen. 2008, 70 (11): 674-678. 10.1055/s-0028-1100401.View ArticlePubMedGoogle Scholar
  9. Laisne F, Lecomte C, Corbiere M: Biopsychosocial determinants of work outcomes of workers with occupational injuries receiving compensation: a prospective study. Work. 2013, 44 (2): 117-132.PubMedGoogle Scholar
  10. Anner J, Schwegler U, Kunz R, Trezzini B, de Boer W: Evaluation of work disability and the international classification of functioning, disability and health: what to expect and what not. BMC Public Health. 2012, 12: 470-10.1186/1471-2458-12-470.View ArticlePubMedPubMed CentralGoogle Scholar
  11. Körner M: ICF und sozialmedizinische Beurteilung der Leistungsfähigkeit im Erwerbsleben: Alles klar? - Ein Diskussionsbeitrag. Rehabilitation (Stuttg). 2005, 44 (4): 229-236. 10.1055/s-2005-866907.View ArticleGoogle Scholar
  12. Bürge E, Cieza A, Allet L, Finger ME, Stucki G, Huber EO: Intervention categories for physiotherapists treating patients with internal medicine conditions on the basis of the International Classification of Functioning Disability and Health. Int J Rehabil Res. 2008, 31 (1): 43-50. 10.1097/MRR.0b013e3282f4525c.View ArticlePubMedGoogle Scholar
  13. Jelsma J: Use of the International Classification of Functioning, Disability and Health: a literature survey. J Rehabil Med. 2009, 41 (1): 1-12. 10.2340/16501977-0300.View ArticlePubMedGoogle Scholar
  14. Hieblinger R, Coenen M, Stucki G, Winkelmann A, Cieza A: Validation of the International Classification of Functioning, Disability and Health Core Set for chronic widespread pain from the perspective of fibromyalgia patients. Arthritis Res Ther. 2009, 11 (3): R67-10.1186/ar2696.View ArticlePubMedPubMed CentralGoogle Scholar
  15. Kirschneck M, Kirchberger I, Amann E, Cieza A: Validation of the comprehensive ICF core set for low back pain: The perspective of physical therapists. Man Ther. 2011, 16 (4): 364-372. 10.1016/j.math.2010.12.011.View ArticlePubMedGoogle Scholar
  16. Soer R, van der Schans CP, Geertzen JH, Groothoff JW, Brouwer S, Dijkstra PU, Reneman MF: Normative values for a functional capacity evaluation. Arch Phys Med Rehabil. 2009, 90 (10): 1785-1794. 10.1016/j.apmr.2009.05.008.View ArticlePubMedGoogle Scholar
  17. Homa DB: Using the International Classification of Functioning, Disability and Health (ICF) in job placement. Work. 2007, 29 (4): 277-286.PubMedGoogle Scholar
  18. Glässel A, Finger ME, Cieza A, Treitler C, Coenen M, Escorpizo R: Vocational rehabilitation from the client's perspective using the International Classification of Functioning, Disability and Health (ICF) as a reference. J Occup Rehabil. 2011, 21 (2): 167-178. 10.1007/s10926-010-9277-x.View ArticlePubMedGoogle Scholar
  19. Salvador-Carulla L, Garcia-Gutierrez C: The WHO construct of health-related functioning (HrF) and its implications for health policy. BMC Public Health. 2011, 11 (Suppl 4(11)): S9.View ArticlePubMedPubMed CentralGoogle Scholar
  20. Duchan JF: Where is the person in the ICF?. Advanc Speech-Language Pathol. 2004, 6 (1): 63-65. 10.1080/14417040410001669444.View ArticleGoogle Scholar
  21. Wade DT, Halligan P: New wine in old bottles: the WHO ICF as an explanatory model of human behaviour. Clin Rehabil. 2003, 17 (4): 349-354.View ArticlePubMedGoogle Scholar
  22. Offenbächer M, Cieza A, Brockow T, Amann E, Kollerits B, Stucki G: Are the contents of treatment outcomes in fibromyalgia trials represented in the International Classification of Functioning, Disability, and Health?. Clin J Pain. 2007, 23 (8): 691-701. 10.1097/AJP.0b013e318148b93d.View ArticlePubMedGoogle Scholar
  23. Cieza A, Stucki G, Weigl M, Kullmann L, Stoll T, Kamen L, Kostanjsek N, Walsh N: ICF Core Sets for chronic widespread pain. J Rehabil Med. 2004, 36 (Suppl 44): 63-68.View ArticleGoogle Scholar
  24. Schult ML, Ekholm J: Agreement of a work-capacity assessment with the World Health Organisation International Classification of Functioning, Disability and Health pain sets and back-to-work predictors. Int J Rehabil Res. 2006, 29 (3): 183-193. 10.1097/01.mrr.0000210057.06989.12.View ArticlePubMedGoogle Scholar
  25. Schwegler U, Peter C, Trezzini B, Anner J, Geyh S: Toward transparent documentation in medical work capacity evaluations: identifying personal factors in medical reports on Swiss disability claimants with chronic widespread pain. Int J Rehabil Res. 2013, 36 (4): 298-307. 10.1097/MRR.0b013e3283618d48.View ArticlePubMedGoogle Scholar
  26. Fayed N, Cieza A, Bickenbach JE: Linking health and health-related information to the ICF: a systematic review of the literature from 2001 to 2008. Disabil Rehabil. 2011, 33 (21–22): 1941-1951.View ArticlePubMedGoogle Scholar
  27. Schwegler U, Anner J, Boldt C, Glässel A, Lay V, De Boer WE, Stucki G, Trezzini B: Aspects of functioning and environmental factors in medical work capacity evaluations of persons with chronic widespread pain and low back pain can be represented by a combination of applicable ICF Core Sets. BMC Public Health. 2012, 12 (1): 1088-10.1186/1471-2458-12-1088.View ArticlePubMedPubMed CentralGoogle Scholar
  28. Cieza A, Stucki G, Weigl M, Disler P, Jäckel W, van der Linden S, Kostanjsek N, de Bie R: ICF Core Sets for low back pain. J Rehabil Med. 2004, 36 (44 Suppl): 69-74.View ArticleGoogle Scholar
  29. Cieza A, Chatterji S, Andersen C, Cantista P, Herceg M, Melvin J, Stucki G, de Bie R: ICF Core Sets for depression. J Rehabil Med. 2004, 36 (Suppl 44): 128-134.View ArticleGoogle Scholar
  30. Stucki A, Daansen P, Fuessl M, Cieza A, Huber E, Atkinson R, Kostanjsek N, Stucki G, Ruof J: ICF Core Sets for obesity. J Rehabil Med. 2004, 36 (Suppl 44): 107-113.View ArticleGoogle Scholar
  31. Lee F, Peterson C: Content analysis of archival data. J Consult Clin Psychol. 1997, 65 (6): 959-969.View ArticlePubMedGoogle Scholar
  32. Patton M: Qualitative evaluation and research methods. 1990, Newbury Park: SageGoogle Scholar
  33. Coenen M: Developing a method to validate the WHO ICF Core Sets from the patient perspective: rheumatoid arthritis as a case in point. PhD thesis. 2008, Munich: Ludwig-Maximilians-UniversityGoogle Scholar
  34. Cieza A, Brockow T, Ewert T, Amman E, Kollerits B, Chatterji S, Üstün TB, Stucki G: Linking health-status measurements to the international classification of functioning, disability and health. J Rehabil Med. 2002, 34 (5): 205-210. 10.1080/165019702760279189.View ArticlePubMedGoogle Scholar
  35. Cieza A, Geyh S, Chatterji S, Kostanjsek N, Üstün B, Stucki G: ICF linking rules: an update based on lessons learned. J Rehabil Med. 2005, 37 (4): 212-218. 10.1080/16501970510040263.View ArticlePubMedGoogle Scholar
  36. Kottner J, Audige L, Brorson S, Donner A, Gajewski BJ, Hrobjartsson A, Roberts C, Shoukri M, Streiner DL: Guidelines for Reporting Reliability and Agreement Studies (GRRAS) were proposed. J Clin Epidemiol. 2011, 64 (1): 96-106. 10.1016/j.jclinepi.2010.03.002.View ArticlePubMedGoogle Scholar
  37. Geyh S, Cieza A, Bickenbach JE, Stucki G: ICF Personal Factors Preparatory Outline. 2009, Nottwil: ICF Research BranchGoogle Scholar
  38. Grotkamp SL, Cibis WM, Nüchtern EAM, von Mittelstaedt G, Seger WKF: Personal Factors in the International Classification of Functioning, Disability and Health: Prospective Evidence. Aust J Rehabilitation Couns. 2012, 18 (1): 1-24. 10.1017/jrc.2012.4.View ArticleGoogle Scholar
  39. Pre-publication history

    1. The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1472-6963/14/361/prepub

Copyright

© Schwegler et al.; licensee BioMed Central Ltd. 2014

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Advertisement