Study design

This longitudinal prospective cohort study was embedded within a three armed RCT with an educational intervention in a primary care setting [16]. The cohort encompasses all patients enrolled in the trial. The primary goal of the RCT was to asses the impact of treatment on functional capacity. A predefined secondary goal of the study was to explore the variation of health care services for LBP. The intervention consisted in quality circles for general practitioners (GPs) on an evidence-based LBP guideline (in both intervention arms) and in training of practice nurses in motivational counselling to promote physical activity (in one intervention arm). The guideline is in accordance with the European guidelines [17, 18]. These guidelines do not advocate acupuncture for LBP, but rather consider the treatment method as a second line intervention with uncertain effectiveness. The study was conducted in two centres (Marburg, Göttingen). Ethical approval was obtained from both study sites.

General practitioners

The goal was to recruit 120 practices. In all practices, both GPs and practice nurses had to agree to participate in the educational intervention, in case they would be randomized to the intervention arm with motivational counselling. We contacted 818 general practices surrounding the study centres. Addresses were obtained from local health authorities. From 118 practices who agreed to participate, 2 dropped out after randomization. The GPs were on average 12.7 years in practice (Range 1 to 31 years), the average age was 48 years (SD ± 6) (national average 50.4 years) and 42 % of them were female (national average 36 %). A total of 68 (59 %) practices were run by a single GP. The basic demographic data of our sample is not meaningfully different from the national average [19]. Of the 116 participating practices, 25 (21 %) offered acupuncture treatment to their patients.

Patients

During the recruitment period of 8 weeks, practice nurses asked every patient with LBP to participate in the study and registered these individuals in order to estimate the number of screened patients. Patients were recruited form November 2002 to March 2003. Inclusion criteria were (1) consulting for LBP in general practice, (2) age above 18, (3) ability to read and understand German and (4) written consent.

Instruments and data collection

After written consent was obtained, baseline socio-demographic data was collected prior to the consultation with a baseline questionnaire. In addition, patients mailed a questionnaire filled in at home to the study centres. During the consultation, GPs assessed warning signs for complicated LBP ("red flags"). At follow-ups 4 weeks, 6 months and 12 months later, study nurses conducted standardised telephone interviews and patients were asked about health care utilization.

The Hanover Functional Ability Questionnaire (HFAQ) was used for the assessment of functional capacity. The HFAQ is a frequently used instrument for the assessment of back pain disability and a scale with good psychometric properties. It consists of 12 items in which patients can rate their limitation in day-to-day functional abilities. It can be compared to the Roland & Morris Scale, but is advantageous in telephone interviews [20]. The scale ranges from 0 (extreme functional limitation) to 100 (no functional limitation), scores below 70 are considered to be a significant impairment.

In order to classify the natural history of LBP, we used a modification of the von Korff procedure as follows [21]:

▪ Acute LBP single episode of LBP of less than 90 days duration

▪ Recurrent LBP multiple episodes LBP of less then 90 days duration within the last 12 months

▪ Chronic LBP more then 90 consecutive days of LBP within the last 12 months.

To estimate the proportion of patients with radicular symptoms, we relied on the reported level of pain radiation into the leg. We considered radiation below the knee as an indicator of possible nerve root irritation. This is a frequently used and pragmatic approach given the absence of reliable methods for assessing radicular pain in large cohorts [22].

For assessment of depression, we applied the German version of the Centre for Epidemiologic Studies Depression Scale (CES-D) [23]. Scores above 23 are considered clinically relevant [24].

In the telephone interview, we also collected data on health care utilisation, e.g. specialist visits, medication, and non-pharmacological treatment for LBP within the last 6 months. In the interview, the study nurses actively presented a list of 42 possible interventions for LBP. They were trained in conducting standardized interviews and able to describe each method in more detail if necessary. Acupuncture sessions were not considered as consultations. We asked them whether they had received injections in the back or in the buttocks. Injections in the back most likely indicate the use of local anaesthetics with or without steroids, injections in the buttocks most likely indicate the application of an analgesic medication.

Statistical analysis

In a first step, we conducted univariate analyses in order to compare patients who received acupuncture with those who did not. In case of missing data, we provide the number of subjects analysed. Dependent on the biometric properties of the scales, we either used chi²-tests for categorical data, or t-tests and non-parametric tests (Kruskall-Wallis) for continuous data. We considered data to be statistically significant at a 5 % level. A calculation of odds ratios allowed to depict 95 % confidence intervals (CI). When data for health care utilization was missing, it was assumed that patients did not receive that particular service.

In a second step, we performed logistic regression analyses. This procedure calculates the probability of receiving or using a specific health service in relation to acupuncture. Only those factors were incorporated into the model that had proved to be significant in previous univariate tests (chronicity, duration of pain, CES-D score, radiation of pain below the knee, baseline HFAQ). Continuous data were dichotomised. For depression we used a cut-off score of >23 and for functional capacity (HFAQ) a cut-off score of > 70. Due to missing data, the models included only 1320 (98 %) patients.

Given the fact that the present study was an embedded cohort study, we also checked if one of the study arms was a significant factor in the model, which was not the case.

Comparison of consultation frequencies and duration of sick leave were adjusted with ANCOVA including the same covariates as the logistic regression models.

In a final step, we calculated a comprehensive model to predict the probability of receiving acupuncture. This model included all of the factors that had demonstrated their significance in previous univariate analyses. This model included only 1163 (87 %) subjects due to list wise deletion. The software package SAS 9.1 was used for analysis.

Patients

Only 60 % of the practices returned registration lists filled in correctly. From this data, it is estimated that approximately 3,400 patients with LBP had been invited to participate. Of those 1,588 patients who agreed to participate, 1,345 were finally included. Reasons for exclusion are listed in Figure 1. The participating 116 practices recruited on average 11.6 (SD ± 5.8) consecutive patients over a period of two months. A total of 1,218 patients were followed up for one year. Overall, 127 patients (9.4 %) dropped out of the study. During the one-year follow-up, 179 (13 %) participants received acupuncture for LBP, 97 at one period, 63 patients at two periods and 18 patients during the entire follow-up. The number of acupuncture sessions ranged from 1 to 47, mean 12 (SD ± 8.8).

Socioeconomic baseline data

Disease-related data

Health service utilisation

Patients receiving acupuncture had a significantly higher adjusted consultation rate both for GPs and for specialists. Regarding GPs, their rate was 15.6 (CI 13.8–17.6) visits a year versus 9.5 (CI 8.7–10.2) visits a year (p < .001). Regarding specialists, the rate was 13.1 (CI 11.6–14.5)/year versus 3.5 (CI 3–4.2)/year (p < .001). They were OR 3.2 (CI 2–5.2) times more likely to consult a specialist. More then 90 % of the specialists were orthopaedic surgeons. Those acupuncture patients who were part of the work force had not been more frequently on sick-leave after adjustment, but for a significantly longer period of time: 31.8 (CI 23–40.1) days a year versus 16.1 (CI 12.9–19.4) days a year after adjustment (p < .001).

Prediction model for receiving acupuncture

Those GPs who offered acupuncture had recruited 280 patients altogether. 66 (23,6%) of them had actually received this treatment (OR 2.7 (CI 1.9–3.8)). Most of the acupuncture patients (n = 110, 62 % of them), however, had been given the treatment by specialists, the majority of them orthopaedic surgeons.

To explore the role of provider related factors for the provision of acupuncture, we included two variables in a logistic regression model: (1) consulting one of the GPs or (2) consulting one of the specialists that provided acupuncture service. We controlled for socio-demographic and disease-related factors that had been proven to be associated with acupuncture in previous univariate analyses. The results show that consulting such a GP (OR 3.5 (CI 2.9–4.1)), consulting such a specialist (OR 2.1 (CI 1.9–2.3)), and the state of pain chronicity (OR 1.6 (CI 1.4–2.9)) were the only factors significantly associated with receiving acupuncture. Gender, age, radiation of pain, functional capacity, and depression did not contribute to explaining determinants of the treatment.

Summary of main findings

Our study supports the hypothesis that receiving acupuncture for LBP seems to be rather a function of availability and to a lesser degree dependant on disease-related factors (like pain chronicity). In univariate analyses, patients receiving acupuncture tended to be older and therefore more often retired. They were more likely to be female, while income and education did not predict the application of the treatment. The majority of patients receiving acupuncture also had chronic LBP. In about one third of our sample, acupuncture was probably inappropriate due to the lack of evidence of effectiveness for acute and recurrent LBP. After adjustment for those baseline differences that may partly explain the increased use of health care services for the acupuncture group, acupuncture remained associated with an increased frequency of consultations and of other therapies for LBP.

Strengths and limitations

This is to date the largest prospective cohort study in Germany that provides clinical data in a population of patients with LBP in this country. Due to the fact that practice nurses also had to agree to participate in the trial, we anticipated a relatively low practice recruitment rate. The sample size and the demographic baseline data of participating GPs make us confident that the data we collected is representative of current clinical practice in Germany. Unfortunately, we do not know how many patients were offered acupuncture and how many of them declined to accept the treatment e.g. due to co-payment or other reasons. Since we do not know if acupuncture was given by the GP or a specialist, we might overestimate the proportion of GPs who contributed to a patient's receiving acupuncture. Nevertheless, a proportion of 13 % of subjects receiving acupuncture is remarkable in a primary care setting for an intervention not covered by the statutory health insurance. Another limitation is that we do not know which method was used for acupuncture and the qualification of the providers. Acupuncture is not a standardized method and may have been applied in various ways. One should keep in mind that the study is a post hoc analysis and was not designed to assess the effectiveness of acupuncture.

Comparison with other studies

Our findings that females and patients with chronic LBP were more likely to receive acupuncture are not surprising. From other surveys, it is known that women are more prone to try acupuncture [25]. Being male and being in a state of good health was found to be associated with a disregard of complementary alternative medicine (CAM) [26]. In the United Kingdom, higher income was associated with use of CAM [27]. This relation obviously depends on access and coverage provided by the health care system. Since co-payment for acupuncture was required in Germany, we expected low income or unemployment to be associated with less acupuncture, which – contrary to our expectation – was not the case. This could partly be due to the reason that some patients participated in the afore mentioned acupuncture initiative. Ample time and the willingness to adhere to repeated treatment sessions may also be an issue, since retired individuals were more likely to receive acupuncture. Although these factors contribute to explain the participation in acupuncture treatment, there may be other factors we were not able to explore in this study, like previous experience with acupuncture, dissatisfaction with conventional treatment and comorbid conditions.

It has been argued that offering acupuncture services reduces the need for other services like e.g. physiotherapy [12]. The above-mentioned randomized controlled trials found acupuncture to be cost effective partly due to the reduced use of other health care services [12, 13]. Our data suggests that receiving acupuncture does not offset the use other health care resources. Contradictory, in our study, acupuncture was associated with increased GP consultation rates, specialist consultations, and prescriptions for physiotherapy. Acupuncture patients were also more likely to receive other (controversial) treatment options like manual therapy, transcutaneous electric nerve stimulation (TENS) and injection therapies. These treatments are considered to be ineffective or of unproven effectiveness and are not recommended by evidence-based guidelines [16, 17].

Patients with disabling, recurrent or chronic LBP are more likely to consult a specialist and to need services like pain medication or physiotherapy. The association between an increased use of health care resources and acupuncture is only partly explained by the disease-related factors we collected. Receiving acupuncture seems to be a surrogate parameter for high health service utilisation and might reflect a feeling of helplessness in both patients and health care providers. Nevertheless, the most important factor determining acupuncture treatment is consulting a GP who offers the treatment or a specialist.