Volume and Quality of Procedures Are Not Necessarily Correlated

BY TIMOTHY F. KIRN

SAN FRANCISCO -- The generalization that the more procedures a hospital does, the better it is, may be an oversimplification at best and misleading at worst, according to two studies presented at the annual clinical congress of the American College of Surgeons.

In one study, Dr. Melissa A. Meyers and coinvestigators compared colectomy mortality in rural hospitals with that in urban hospitals, using Medicare data on 279,385 patients who had surgery between 1994 and 1999. Overall mortality was the same in the two groups. In small rural hospitals with a low volume of procedures, the mortality rate was 6.7%. In urban hospitals, most of which had higher volume, the rate was 6.4%, said Dr. Meyers of the surgery department at Dartmouth-Hitchcock Medical Center, Lebanon, N.H.

Analysis of the data did show some evidence that the more colectomies a hospital performed the lower the mortality, but that observation held only for the urban hospitals. Rural hospitals had no such correlation between volume and mortality, though 90% of the rural hospitals had a low volume. Moreover, the mortality at the rural hospitals was not much different from that at the best urban hospitals, where the rate was 5.6%.

"Hospital procedure volume is a poor proxy for quality in a rural setting, and we need to develop better ways to gauge quality in hospitals overall," Dr. Meyers said.

In the second study, Dr. Dharam Kumbhani and colleagues looked at 30-day mortality for 10 different surgical procedures in the Veterans Administration system. The study used data from the Veterans Affairs (VA) National Surgical Quality Improvement Program. The study, which looked at procedures of intermediate to high complexity, ranging from carotid endarterectomy to pancreaticoduodenectomy, found no relationship between low volume and worse outcome, said Dr. Kumbhani of the VA Boston Healthcare System.

In 8 of the 10 surgical procedures, there was a statistically significant relationship between low volume and the observed-to-expected ratio of 30-day mortality. This difference was not clinically significant, Dr. Kumbhani said. When the data were analyzed with a hierarchical model that accounted for patient and hospital factors, no relationship was seen between volume and 30-day mortality.

"We believe that systems of care are much more important than volume in determining the quality of surgical care," Dr. Kumbhani said. The findings of his study are particularly robust and are probably more accurate than other studies of volume and surgical outcome, because the VA program collects all of its data prospectively and was designed for just this type of analysis, he added. During the animated discussion period, it was suggested that the studies should serve as a cautionary note to efforts to measure quality solely in terms of volume, because the volume-quality equation perhaps only holds for very sophisticated procedures such as transplants.

However, Dr. Justin Dimick of the Veteran's Affairs Medical Center in White River Junction, Vt., who was a designated discussant for the VA study, took issue with generalizing its results, which are at odds with an extensive body of research showing that the more a surgeon or a hospital does a particular procedure the better they are at it. "The VA is a different health care system than you see in the private sector," he said.

When asked to comment upon this story, Dr. John W. Hallett, medical director and vascular surgeon and clinical professor of surgery at the Roper St. Francis Heart and Vascular Center, Charleston, S.C., stated: 'This comparison of rural and urban hospitals confirms what many experienced surgeons believe. Good outcomes come more from a practiced system of surgical care with a consistent operating and postoperative team than just from the volume of cases. When it comes to new technologies in surgery, volumes of cases are often low at first and a consistent surgical team with quality improvement processes remains the key to good outcomes. Systems and teamwork generally outweigh sheer volume in any situation," Dr. Hallett said.