WASHINGTON –  Despite the rapid growth of retail clinics, only a tiny fraction of American families in 2007 used them, according to the Commonwealth Fund.

The number of retail clinics, typically located in pharmacies, supermarkets and big-box retailers, has grown rapidly in recent years, from 60 in 18 states at the beginning of 2006 to more than 900 in 30 states by late 2007.

"While overall use of retail clinics remains modest, families with unmet medical needs tend to use the clinics more than the rest of the population," said Ha T. Tu, an HSC senior researcher and co-author of the study with Genna R. Cohen, a Health Systems Change health research assistant.

As of 2007, 2.3 percent of American families, or nearly 3.4 million families, have used a retail clinic, according to findings from HSC's 2007 Health Tracking Household Survey, a nationally representative survey with information on about 18,000 people in 9,400 families.

"They are well-received by patients, covered by health plans, and perceived as being somewhat threatening by local doctors and hospitals, who see their potential to siphon-off business," said Paul H. Keckley, executive director of the Deloitte Center for Health Solutions, in a paper titled "Retail Clinics: Facts, Trends and Implications."

Nearly half of all clinic users cited the low cost of a clinic visit relative to other care settings and one in three cited not having a usual source of medical care as major reasons for choosing clinics.

The study found that families that reported not getting or delaying needed medical care in the previous 12 months were almost 2.5 times as likely to have used a retail clinic as families without such problems.

"These findings suggest that retail health clinics have the potential to play a role in improving healthcare delivery, especially primary care," said Commonwealth Fund Vice President Anne-Marie Audet, MD.