Primary care and behavioral health practice size: the challenge for health care reform.

INTRODUCTION: We investigated the size profile of US primary care and behavioral health physician practices since size may impact the ability to institute care management processes (CMPs) that can enhance care quality.
METHOD: We utilized 2009 claims data from a nationwide commercial insurer to estimate practice size by linking providers by tax identification number. We determined the proportion of primary care physicians, psychiatrists, and behavioral health providers practicing in venues of >20 providers per practice (the lower bound for current CMP practice surveys).
RESULTS: Among primary care physicians (n=350,350), only 2.1% of practices consisted of >20 providers. Among behavioral health practitioners (n=146,992) and psychiatrists (n=44,449), 1.3% and 1.0% of practices, respectively, had >20 providers. Sensitivity analysis excluding single-physician practices as "secondary" confirmed findings, with primary care and psychiatrist practices of >20 providers comprising, respectively, only 19.4% and 8.8% of practices (difference: P<0.0001). In secondary analyses, bipolar disorder was used as a tracer condition to estimate practice census for a high-complexity, high-cost behavioral health condition; only 1.3-18 patients per practice had claims for this condition.
CONCLUSIONS: The tax identification number method for estimating practice size has strengths and limitations that complement those of survey methods. The proportion of practices below the lower bound of prior CMP studies is substantial, and care models and policies will need to address the needs of such practices and their patients. Achieving a critical mass of patients for disorder-specific CMPs will require coordination across multiple small practices.