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Table 2 COC index measures used in the studies to investigate associations between COC, healthcare use and costs

From: Association between continuity of care (COC), healthcare use and costs: what can we learn from claims data? A rapid review

Measure

Description

Range

Concept *

Formula

Interpretation

Number of papers using this index

1.Bice & Boxerman index (COCI)

the degree to which patient visits are distributed among different physicians

0 (all visits to different providers) to 1 (all visits to the same provider)

dispersiona

densityb

\(\large \frac{{\sum }_{i=1}^{M}{n}_{i}^{2}-N}{N(N-1)}\)

N-total number of visits, ni number of visits with provider i, M-total number of providers

35

2.Usual Provider of Care (UPC)

the proportion of visits with a usual provider

0 (no visits to the usual provider) to 1 (all visits to the usual provider)

density

\(\large \frac{{{max}_{i=1,\dots M} n}_{i}}{N}\)

N- total number of visits, ni – number of visits with provider i, M-total number of providers

14

3.Most Frequent Provider Continuity (MFPC) (similar to UPC)**

defines the primary provider as the one seen most frequently

0 (no visits to the provider) to 1 (all visits to this providermost frequent provider)

density

\(\large \frac{max({n}_{1},{n}_{2}\dots , {n}_{M})}{N}\)

N - total number of visits, ni - number of visits with provider i (i=1,…M), M-total number of providers

2

4.Modified, Modified Continuity Index (MMCI)

the extent to which a patient concentrated her/his visits with the same healthcare provider

0 (all visits to different providers) to 1 (all visits are to the same provider)

dispersion

\(\large \frac{1-\frac{M}{N+0.1}}{1-\frac{1}{N+0.1}}\)

M -number of different providers and N- total number of visits.

5

5.Sequential Continuity of Care index (SECON)

the proportion of sequential visits that were with the same provider, i.e. same provider being seen at both the previous and current visits

0 (no sequential visits to the same provider) to 1 (all sequential visits to the same provider)

sequential c

\(\large \frac{{\sum }_{j=1}^{n-1}{\text{c}}_{\text{j}}}{n-1}\)

if the visit j and the subsequent visit (j + 1) are to the same provider then cj = 1, and cj = 0 if otherwise; n-1- sequential pairs of visits

5

6.Herfindahl Index

indicator of provider concentration, physician’s share of a patient’s visits.

0 (less-dominant providers, not concentrated) to 1 (all visits to the same provider, very concentrated)

concentrationd

\(\large {\sum }_{i=1}^{M}{\left(\frac{{n}_{i}}{N}\right)}^{2}\)

ni - visits for patients to an individual provider i, and N - total number of visits, M-total number of providers

1

7.Care density

reflect how frequently patient’s doctors collaborate/ share patients with one another

0 (no collaboration/ no shared patients) to ∞ (extreme collaboration/ all patients of all doctors are shared)

density; level of shared patients between providers

\(\large \frac{{\sum }_{i=1}^{m}{\text{w}}_{\text{p,i}}}{{\text{M}}_{\text{p}}({\text{M}}_{\text{p}}-1)/2}\)

Mp - number of distinct doctors that patient p saw, m - total number of possible pairs of doctors, and wp,i - number of shared patients for each pair of doctors. The numerator is the total number of instances of patient sharing over a time period (e.g. a year) among a patient’s doctors. The denominator is the total number of pairs of doctors for that patient.

3

8.Clinician Index

the proportion of visits with primary clinician out of all ambulatory visits

0 (no visits to the primary clinician) to 1 (all visits to the primary clinician)

density

np/Na1

np - number of ambulatory visits to a primary clinician and Na1 - number of ambulatory visits in the 1st year

1

9.Site Index

the proportion of visits with primary site out of all visits

0 (no visits to the primary site) to 1 (all visits to the primary site)

density

np/N1

np - number of visits to a primary site and N1 - total number of visits in the 1st year

1

Compound Indices

10.Integrated Continuity of Care index (ICOC)

ICOC is a linear combination of three indices UPC, COC, SECON via Principal Component Analysis (PCA)

0 (no visits to the same provider) to 1 (all visits to the same provider)

dispersion; density; sequence

ICOC=(β1 UPC+ β2COC+β3SECON)/ (β1+ β2+ β3)

ß1, ß2, and ß3 is the first principal component Eigenvector of the PCA result, which used the weighted means of the variables for each type of index

1

11.Composite index (COMP)

Composite index, derived by adding the score values of the four commonly used COC indices (COCI, UPC; MMCI, SECON) and dividing by four

0 (no visits to the same provider) to 1 (all visits to the same provider)

dispersion, density, sequence

(UPC+COCI+MMCI+SECON)/4

UPC - usual provider of care index, COCI - Bice& Boxerman index, MMCI - Modified modified continuity index, SECON - sequential continuity index

1

12.CI Alpha Index

weighted average of the concentration of providers seen and sequential continuity; KL represents Kullback-Leibler information index showing the degree of concentration relative to no concentration at all

0 (a different provider is seen for each patient visit, maximum dispersion in both provider concentration and visit sequence) to 1(the same provider is seen at every visit)

concentration and sequence

CIα = αKL* + (1 - α) SECON,

α ϵ [0, 1];

\(KL= log M+ {\sum }_{i=1}^{M}\frac{{n}_{i}}{M} \times log \frac{{n}_{i}}{M}\);

and

\(KL*=\frac{KL}{\mathit{log}M}\)

α is a predetermined weight that is applied to both KL* and SECON; M - total number of providers and ni is number of visits with provider i.

1

  1. PCA Principal Component Analysis
  2. *concept according to the typology developed by Jee and Cabana[7]
  3. **indices UPC and MFPC were used as independent in the source studies
  4. aThe dispersion of visits among various providers
  5. bThe density of visits with a provider
  6. cThe number of handoffs of information required between providers
  7. dThe concentration of visits with a particular provider