When people are ranking hospitals for quality in teaching and handling cases referred from other institutions, Maine Medical Center is near the top of the list for New England in many areas, and among the top in the nation in more than one.

Its reputation for cardiac, cancer and orthodpedic care is among the best in the United States, for example.

That’s why it was both surprising and a bit of a shock to see that, on the basis of an 18-month study that ended in June 2009, it had experienced twice the national rate of dangerous blood infections from large intravenous catheters. (Such tubes are inserted through a large central vein to a blood vessel near the heart to deliver fluids, medication or nutrition, and can stay in place for long periods of time.)

In fact, MMC ranked first among the state’s larger hospitals in its rate of such infections. That’s a significant finding, but it’s not something that should make people assume that care at MMC is significantly flawed.

Sometimes doing relatively worse on a comparative scale of care merely means that the institution in question takes in more seriously ill patients, many of whom would have poorer outcomes no matter where they were treated. Or, as in this case, more patients are admitted who need large intravenous catheterization for longer periods of time, and thus a higher rate of infections is inevitable.

That’s what MMC officials say about their care. Many of their patients require feeding through such catheters, which raises the odds of infection.

They also say that they have improved the rate at which they are complying with processes designed to reduce the incidence of infections, and since the study period ended, the rate of infections has fallen from 4.2 per 1,000 patient catheter days to 2.7, nearer the national large-teaching-hospital rate of 2.1.

That shows, among other things, that publicizing comparative statistics is worthwhile. Not only is the public informed, but institutions whose performance on a given standard is below average have a strong incentive to improve. Of course, averages aren’t the whole story. If all hospitals do poorly on one type of patient care, being average is no accomplishment.

Still, MMC paid attention and is doing better in this area. Thus, so are its patients. That’s what it’s all about.