Birth Certificate Validity and the Impact on Primary Cesarean Section Quality Measure in New York State

In New York (NY), birth certificate data are routinely used for assessing quality of care and health outcomes such as primary cesarean section (PCS) rates. However rare events are often underreported. This study compared birth certificates to medical records, and examined the impact of underreporting on risk adjustment variables for PCS. We conducted an internal validation study using a random sample of 702 NY births in 2009. Sensitivity and positive predictive value (PPV) of rare events reported on birth certificates were determined using abstracted and matched medical records as the gold standard. To assess the impact, we calculated PCS odds ratios for variables in the risk-adjustment model before and after correcting for measurement error. The sensitivity and PPV of birth certificate data elements including those in the PCS risk model varied from 0 to 100. After correction for measurement error, PCS odds ratios increased for most variables. For example, the PCS odds ratio for those with no prior live births was 3.03 (95% CI 2.94, 3.13), but after correction of measurement error increased to 3.46 (95% CI 3.22, 3.67). A composite negative event variable including abruptio placenta, eclampsia, or infection was the only variable that decreased after correction and was no longer significant (uncorrected OR 3.06, 95% CI 2.86, 3.29; corrected OR 1.42, 95% CI 0.79, 2.59). Underreporting on birth certificates remains concerning and impacts the risk adjustment for quality measures. Without improved data validity, health plans' quality metrics do not fully account for patient case-mix.