Retail-based health clinics, such as MinuteClinic, which are staffed by nurse practitioners, are filling a health care niche and offering a low-cost option for minor health problems. Critics say the clinics don't offer the kind of follow-up care needed and some insurers don't cover the visits, but clinic numbers are increasing. "Look at how everyone is talking about universal health care. ... Certainly these clinics could be part of the solution," one CareClinic executive said.