The doc in the store is gaining on traditional primary care providers.

Ateev Mehrota, a healthy policy analyst at the RAND Corp., Santa Monica, Calif., and Judith Lave, a health policy economist at the University of Pittsburgh, look at U.S. consumers’ use of retail health clinics in a paper published behind a paywall by Health Affairs, an academic journal that focuses on health care finance and health care delivery.

Mehrota and Lave defined retail clinics as medical offices in pharmacies, grocery stores and other retail settings.

Patients made more than 6 million visits to the clinics in 2009, up from 1.5 million visits in 2007, the analysts say.

The analysts based those figures on data from three large clinic operators — MinuteClinic, TakeCare and Little Clinic. Those companies run about 81% of the U.S. retail clinics, the analysts estimate.

The analysts compared the 2007-2009 records with three big clinic operators’ records from 2000 through 2006. The companies handled 1.4 million clinic visits from 2000 through 2006.

Patients made 117 million visits to emergency rooms in 2009 and 577 million visits to traditional physician offices that year. Patients visited the retail clinic visits about 0.9% as often as they visited the emergency rooms and traditional physician offices.

The percentage of patients using the retail clinics for preventive care increased to 48% in the 2007-2009 period, from 22% in the 2000-2006 period.

The share of visits involving acute care fell for all conditions studied, but the share of visits involving chronic disease care increased to 1.1% in 2007-2009, from 0.1% in 2000-2006.

The analysts estimate the clinics generated an average of $78 in revenue per visit in 2009, for total revenue of about $460 million.

The Patient Protection and Affordable Care Act of 2010 (PPACA) could increase use of retail clinics, by increasing demand for traditional physician practices’ services, the analysts say.

But, even if PPACA increases demand for traditional practices’ services, “many health care systems and private companies have begun offering online care, or eVisits,” the analysts say. “Such online visits could compete with retail clinic visits and slow the clinics’ growth.”