VOA常速英语:Surgery Outcomes Depend On Multiple, Unidentified Factors

In recent years, a virtual library of medical research has concluded that, other factors being equal, complex surgery turns out better when it's done at hospitals where the procedure is done a lot. Now, a new study suggests it's not that simple.

Lung transplants are seriously complex surgeries, often performed on desperately sick patients. Of thousands of hospitals in the United States, only 61 are authorized to do lung transplants. And some do it better than others.

One measure of success is the five-year survival rate, and the lead author of a new study says that number varied dramatically among the different medical centers doing lung transplants.

"And what we found is that there was a large variability in outcome among centers, that ranged between 30 percent at five years and 60 percent at five years," said Mayo Clinic researcher Gabriel Thabut.

He and his colleagues reviewed 20 years of records from more than 15,000 transplants. Some high-volume hospitals did as many as 120 transplants a year; other medical centers did only one. Success rates varied a lot, but according to their statistical analysis, only about one-eighth of the success depended on how many transplants the hospital did a year.

They report their findings in JAMA, the journal of the American Medical Association.

In an accompanying editorial, Edward Livingston of the University of Texas says the relatively small influence of volume on success of the transplants raises a big question.

"The remaining 88 percent of the variation from one [medical] center to another are unmeasured factors, that we don't quite know what those factors are."

The paper's authors tried to take into account other factors, but they admit it may not have been entirely possible to quantify differences in, for example, the recipient's health, which can be a big factor in the success of a transplant.

In the meantime, Thabut says it's important to focus on the details that separate the most successful transplant hospitals from the rest.

"We have to go to the best centers and try to identify specific practices at these centers that could be exported to lower performing centers."

Both the author and the editorial writer suggested that looking at volume of surgery alone may not be the best way of predicting surgical success.