Ascertainment of medicaid payment for delivery on the iowa birth certificate: is accuracy sufficient for timely policy and program relevant analysis?

The Iowa Department of Public Health annually links Medicaid claims data to the birth certificate. Because the latest version of the birth certificate provides more timely and less costly information on delivery payment source, we were interested in assessing the validity and reliability of the birth certificate payment source compared to Medicaid paid claims. We linked Medicaid paid claims to birth certificates for calendar years 2007-2009 (n = 120,626). We measured reliability by Kappa statistic and validity by sensitivity, specificity, predictive value positive and negative. We examined reliability and validity overall and by maternal characteristics (e.g. age, race, ethnicity, education). The Kappa statistic for the birth certificate payment source indicated substantial agreement (0.78; 95 % CL 0.78-0.79). Sensitivity and specificity were also high, 86.3 % (95 % CL 86.0-86 6 %) and 91.9 % (95 % CL 91.7-92.1 %), respectively. The predictive value positive was 87.0 %. The predictive value negative was 91.4 %. Kappa and specificity were lower among women of racial and ethnic minorities, women younger than age 24, and women with less education. The overall Kappa, sensitivity and specificity generally suggest the birth certificate payment source is as valid and reliable as the linked data source. The birth certificate payment source is less valid and reliable for women of racial and ethnic minorities, women younger than age 24, and those with less education. Consequently caution should be exercised when using the birth certificate payment source for monitoring service use by the Medicaid population within specific population subgroups.