CHICAGO—Hospital comparisons that fail to account for patient characteristics that increase the likelihood of Cesarean delivery may be methodologically biased and may mislead health care purchasers, according to an article in a recent issue of The Journal of the American Medical Association (JAMA).

David C. Aron, M.D., M.S., of Case Western Reserve University in Cleveland, and colleagues studied the impact of adjusting hospital Cesarean delivery rates for risk factors that may increase the likelihood of a Cesarean delivery among 21 Cleveland-area hospitals.

They write: “Cesarean delivery is indicated for many clinical scenarios, and numerous studies have identified patient-specific factors, such as maternal age, breech presentation, placental abnormalities and fetal distress, that are epidemiologically related to increased likelihood of a Cesarean delivery. However, most hospital and health plans comparisons have not accounted for such factors.”

Hospitals and health plans are often ranked on rates of cesarean delivery, under the assumption that lower rates reflect more appropriate, efficient care. However, most rankings do not account for patient factors that affect the likelihood of Cesarean delivery. Cesarean delivery is currently the most commonly performed major surgical procedure in the United States. The authors found that after adjusting hospital rates for the presence of 39 clinical factors that may predispose to Cesarean delivery, outlier status changed for five of the 21 hospitals (Outlier status refers to hospitals that have significantly higher or lower rates than the overall rates.)

They continue: “Additionally, the prevalence of the 39 risk factors varied across hospitals, and predicted rates of Cesarean delivery based on the 39 factors varied by more than 60 percent. These findings suggest that hospitals within a single metropolitan region care for different patient populations and that obstetrical case mix varies.

The results suggest that hospital comparisons that do not account for differences in patient mix may be methodologically biased and may provide consumers and other health care purchasers with misleading information." The study revealed the overall cesarean delivery rate was 15.9 percent and varied from 6.3 percent to 26.5 percent in individual hospitals. Adjusted rates varied from 8.4 percent to 22 percent.

The authors add: "Whereas seven hospitals were classified as outliers on the basis of both unadjusted and adjusted rates, outlier status changed for five hospitals (24 percent), including two that changed from outliers to nonoutliers, two that changed from nonoutliers to outliers, and one that changed from high outlier to a low outlier."

The authors found that in 12 hospitals, the relative difference in unadjusted and adjusted rates was greater than 10 percent.