Do Specialized Centers and Specialists Produce Better Outcomes for Patients with Chronic Diseases than Primary Care Generalists? A Systematic Review

Piet N. Post; Jolanda Wittenberg; Jako S. Burgers


Int J Qual Health Care. 2009;21(6):387-396. 

In This Article

Abstract and Introduction


Purpose. Although specialized centers are generally accepted for treatment of relatively uncommon diseases, such as cystic fibrosis, statements regarding the amount of expertise or minimum number of patients treated are increasingly included in guidelines for the treatment of other chronic diseases such as rheumatoid arthritis and diabetes mellitus.
Data sources. Medline and Embase from 1987 through March 2008 were searched.
Study selection. Studies reporting the effect of treatment in a specialized or high-volume center or by subspecialists on a clinically relevant outcome.
Data extraction. Two reviewers extracted the data independently and assessed the methodological quality.
Results of data synthesis. We included 22 articles. Two randomized-controlled trials and a quasi-experimental study compared the effect of outpatient team care with traditional outpatient care for patients with rheumatoid arthritis. These studies showed no difference or were inconsistent. Studies on the outcomes of care for diabetic patients (5 prospective or historical cohort studies and 10 retrospective cohort studies) were generally of poor quality. Studies comparing the subspecialist care with the care provided by general internists or primary care providers produced inconsistent results. Similar inconsistency and poor quality were found for three observational studies on cystic fibrosis.
Conclusion. The available literature suggests that among patients with rheumatoid arthritis, diabetes mellitus or cystic fibrosis, outcomes are not superior in specialized centers or with subspecialists compared with other forms of chronic illness care.


Over the past decade, the need for information about the quality of care services has increased. Information on treatment outcomes is usually preferred. However, this type of information is often unavailable and may not always be valid for use as a quality indicator.[1] Instead, process measures of quality, derived from clinical practice guidelines, are widely adopted as indicators of quality.[2] Furthermore, the annual volume of patients treated in a hospital is increasingly used as an indicator of quality. The use of this indicator emerged after Luft et al.[3] showed that hospitals performing more than 200 procedures annually had substantially lower surgical mortality rates for some surgical procedures than lower volume hospitals.

After the volume–outcome relationship was confirmed in more recent studies, the use of volume as surrogate indicator of quality has been promoted by the Leapfrog Group and others.[4] The majority of studies included patients undergoing invasive procedures whose outcomes can be observed shortly after the intervention and are relatively easy to measure. For non-invasive procedures, however, the relationship between volume and outcome is unclear.[5] Yet, statements regarding the amount of expertise and/or the minimum number of patients treated do appear in guidelines concerning other chronic diseases.[6,7] Although several reasons exist to recommend treatment in a specialized center, these statements are usually justified by claiming that specialized centers produce better outcomes.

We wondered whether the available evidence indeed supports better outcomes in specialized centers. Therefore, we set out to review the evidence for a disease with general consensus that treatment should take place (by subspecialists) in a specialized center (cystic fibrosis) as opposed to two chronic diseases for which this is less clear (rheumatoid arthritis and diabetes mellitus). Apart from the value of specialized care, we also reviewed the evidence concerning the value of treatment in a high-volume center. Although specialization and high volume are not synonymous, similar processes may determine their relation with outcome.[8] We were interested whether treatment in a specialized (or high-volume) center (or by subspecialists) results in better outcomes for patients, not whether it results in better process measures. Therefore, we conducted a systematic review of the literature to summarize the evidence on the association between healthcare provision in a specialized center or by subspecialists and the outcome of treatment for these three chronic diseases.


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