Risk adjustment for interhospital comparison of primary cesarean rates

Area of Science:

• Obstetrics and Gynecology
• Health Services Research
• Public Health

Background:

• Cesarean delivery rates vary significantly among hospitals.
• Unadjusted rates may not accurately reflect true variations due to differences in patient populations (case mix).
• Accurate identification of outlier hospitals is crucial for quality improvement initiatives.

Purpose of the Study:

• To develop and validate a method for risk adjustment of hospital-specific cesarean delivery rates.
• To control for variations in case mix when comparing cesarean rates across hospitals.
• To identify hospitals with unusually high or low primary cesarean delivery rates.

Main Methods:

• Analysis of 160,753 births from 1991 Illinois birth certificate data.
• Development of a multivariate model using a 25% sample to predict cesarean delivery probability based on medical and sociodemographic factors.
• Validation of the model on the remaining 75% of data and application to calculate predicted primary cesarean rates for 154 hospitals.

Main Results:

• The final risk-adjusted model accurately predicted primary cesarean rates across a range of hospital rates.
• Thirty-five hospitals (23%) had actual rates exceeding their predicted 95% confidence interval.
• Twenty-seven percent of hospitals in the top quartile of actual rates were performing cesarean deliveries appropriate for their patient population's risk.
• Twenty-three percent of hospitals with higher-than-predicted rates were not in the top quartile of unadjusted rates.

Conclusions:

• Risk adjustment for hospital case mix provides a more accurate method for identifying outlier hospitals compared to unadjusted cesarean delivery rates.
• Risk adjustment should be the initial step in investigating variations in primary cesarean delivery rates.
• This approach aids in understanding true hospital performance and facilitates targeted quality improvement efforts.