Going to a MinuteClinic is cheaper for patients than going to a physician's office or urgent care, but there is no evidence that the advent of the popular retail clinics reduced medical costs overall.

A study published today found prices charged by all providers rose by double digits over the four years tracked, a trend that went against the conventional wisdom that more providers leads to more competition and lower prices.

Getting treated at a MinuteClinic costs an average of $104, which works out to $51 less than in urgent care, $55 less than a physician's office and $279 less than an emergency room, according to an article in the journal Health Affairs.

The study is the first to compare costs per episode of care -- which includes not just the medical exam but also lab and pharmacy costs -- for sore throats, ear infections, sinus infections, pinkeye and urinary-tract infections.

The article studied use of the retail clinics by members of HealthPartners, the third-largest insurer in Minnesota. It compared episodes of care in 2003, before MinuteClinic became part of the health plan's network, with visits in 2004, 2005 and 2006.

It included a total of 628,513 episodes of care, of which 3.2 percent were initiated at a MinuteClinic.

MinuteClinic is the first and still the biggest chain of retail clinics, where nurse practitioners treat common ailments in a retail setting.

While it was expected that more care providers would increase competition and lower costs, the study found that overall costs of care for the five conditions rose 14.1 percent during the four-year period.

The average cost per episode rose 20.3 percent in emergency rooms, 12.7 percent in physicians' offices, 11.9 percent in urgent-care settings and 12.2 percent in MinuteClinics during the three years MinuteClinic was in the HealthPartners network.

"The data does not support the idea that MinuteClinic or other retail clinics has had any negative impact on rising health-care costs," said the study's author, Dr. Marcus Thygeson, an associate medical director at HealthPartners.

Even if a large number of HealthPartners members switched to retail clinics, the immediate savings would be relatively small, Thygeson said.

What tends to happen, he said, is other providers will raise their charges to make up for lost revenue.

The study also found that patients using MinuteClinics were more likely to be female and they were less likely to have chronic illnesses than those who sought care at doctors' offices or urgent care.

Chen May Yee • 612-673-7434