Background: There is a trend towards the consolidation of small primary care practices into larger practices, which potentially have economies of scales for employment of staff and use of information technologies. However, the effects of practice size on quality of care remain unclear.
Objective: The objective of this review was to systematically appraise the effects of practice size on the quality of care in primary care.
Inclusion criteria: All quantitative studies that focused on primary care practices or primary care practitioners were considered. Independent variables were team size or list size; outcome variables were measures of clinical processes, clinical outcomes, or patient reported outcomes.
Search strategy: We searched the following databases: PubMed, CINAHL, EMBASE, Cochrane Library, CRD databases, Proquest Dissertations and Theses, Conference proceedings and Mednar from 1990 to 2010. Searches were restricted to English language. We also searched the reference lists of included studies.
Methodological quality: Methodological quality of the studies was assessed using a modified critical appraisal checklist from the Joanna Briggs Institute. Studies that did not fulfill or were unclear in any of the following criteria were excluded: 1) independent variable measured in a reliable way; 2) outcome variables measured in a reliable way; 3) use of appropriate statistical analysis; or 4) confounding factors adjusted for in analysis.
Data collection: Data was extracted using standardised data extraction forms from the Joanna Briggs Institute.
Data synthesis: A narrative synthesis of the results was conducted.
Results: The search yielded 371 articles. Of these, 34 articles were considered relevant and underwent quality assessment. This resulted in 17 articles (13 studies) being included in the review. All studies reviewed were cross-sectional in design. Eight examined the effects of practice size on clinical processes, one on clinical outcomes, two on patient reported outcomes, one on both clinical processes and outcomes, and one on both clinical processes and patient reported outcomes.Of the ten studies on the association between practice size and clinical processes, three found larger practices to have statistically significantly higher specialist referral rates for eating disorder (Rate ratio=1.11, 95% CI: 1.07-1.16, p<0.001), better adherence to American Academy of Pediatrics (AAP) guidelines (OR=2, 95% CI: 1.11-3.33), and better pneumococcal vaccination coverage (OR=1.45, p<0.0001). Three found statistically significant associations in only selected process measures, while four did not find any association between practice size and clinical processes. Of the latter seven studies, four may be underpowered.The two studies on clinical outcomes did not find any statistically significant association with practice size, although both studies may be underpowered. Of the three studies on patient reported outcomes, one reported statistically significant association between smaller practices and satisfaction with access, two found statistically significant associations in about half of the patient reported outcomes evaluated. However, one of the latter two studies may be underpowered.
Conclusions: There is limited evidence available to support an association between practice size and quality of care in primary care. Although some studies showed that larger practices adhered to or implemented clinical processes better than smaller practices, other studies did not find any statistical significance between practice size and other process measures. None of the studies that examined clinical outcomes found statistically significant associations with practice size. For patient reported outcomes, there was some evidence that smaller practice size was associated with better patient reported access, however the evidence for other patient reported outcomes was inconsistent.
Implications for practice: The findings of this review support the current evidence that smaller practices are comparable to larger practices in clinical performance. However, some evidence suggests that larger practices may perform better in certain process measures, while smaller practices may have better satisfaction in certain patient reported outcomes. With the trend towards larger primary care practices, there may be a trade-off between high quality clinical care and interpersonal care.
Implications for research: Further research needs to be done to ascertain an optimal practice size for primary care to retain the benefits that small and large practices can offer. Future studies should address common methodological limitations such as the lack of power due to small sample sizes, and to account for the effects of clustering and collinearity in statistical analyses.