A while back, I blogged about how medical care varies in quality and quantity across different areas in the United States, as well as the reasons why such "small area variation" might exist. This post looks at the same topic but from a slightly different perspective: to what extent can differences in physician quality (where they were trained and where they currently work) explain the variance in medical care seen across groups of patients and regions?
This isn't an easy question to answer: getting at causal effects of physician quality is really hard. For example, an association between patient outcomes and physician quality could simply reflect the fact that wealthier or smarter patients, who are better able to translate directions from their physician to better health outcomes, happen to choose better doctors themselves. As such, conventional estimates using observational data may be biased.
In a very clever study, Joseph Doyle and co-authors get around this selection issue using a natural experiment methodology. In particular, they utilize the randomization of patients in the Veterans Affairs (VA) system to clinical teams from two academic medical centers. One center happens to be very highly rated and the other not so much. Their results suggest that physician quality matters in terms of costs and length of stay, though not so much for ultimate health outcomes:
Those treated by physicians from the higher-ranked institution have 10-25% shorter and less expensive stays than patients assigned to the lower-ranked institution. Health outcomes are not related to the physician team assignment, and the estimates are precise. Procedure differences across the teams are consistent with the ability of physicians in the lower-ranked institution to substitute time and diagnostic tests for the faster judgments of physicians from the top-ranked institution.