Validity of maternal and infant outcomes within nationwide Medicaid data

The aim of this study is to assess the validity of preeclampsia, congenital cardiac malformations, and persistent pulmonary hypertension of the newborn (PPHN) diagnoses in the US Medicaid Analytic eXtract (MAX), a nationwide health care utilization database that may be useful for perinatal research.

Using the 2000-2007 MAX, we identified more than 1 million pregnancies ending in live birth. We identified potential cases based on claims, reviewed their hospital medical records, and calculated the positive predictive values (PPVs) and 95% confidence intervals (CIs) using records as the reference.

Among 183 women with any preeclampsia diagnoses, the PPV was 66.5% (53.6, 77.4%), but it increased to 94.5% (84.0, 98.3%) for inpatient preeclampsia diagnoses. The PPV for inpatient PPHN diagnoses (N = 82) was 68.3% (57.6, 77.4%), but it increased to 89.6% (CI: 77.8, 95.5%) when restricting to infants not transferred to another facility shortly after birth (N = 48). The PPV for cardiac malformations was 77.6% (65.7, 86.2%) when requiring inpatient codes on more than one date (N = 63).

These PPVs are conservative, particularly when patients were transferred or received outpatient diagnoses, because we reviewed records from a single hospitalization only. PPVs improve with stringent identification criteria, at the cost of sensitivity, and can be used to correct for measurement error.