(A24) Validation study of an ASA prophylaxis variable for preeclampsia prevention

Publication Number: 307

Background: In women at higher risk of preeclampsia (PE), clinical guidelines recommend starting low-dose aspirin (ASA) prophylaxis (81-162 mg daily) at 12-19 weeks’ gestation. PE is characterized by high blood pressure after 20 weeks’ gestation and is associated with adverse pregnancy outcomes. The capture of ASA prophylaxis within administrative health databases can be problematic, however, as ASA is available as an over-the-counter medication. The Better Outcome Registry and Network (BORN) database, a perinatal health registry in Ontario, Canada, includes a variable to capture ASA use for PE prevention. However, this variable has not been formally validated.

Objectives: To validate the ASA prophylaxis for PE variable in the BORN database by comparing it to that documented within an electronic medical record (EMR).

Methods: We completed a validation study of 200 randomly selected women who had a livebirth at St. Michael’s Hospital (SMH) in Toronto, Ontario from January 1, 2018, to July 31, 2022. ASA prophylaxis use in pregnancy, including dose and indication for use, and maternal sociodemographic characteristics, were independently extracted by two abstractors. For women with multiple deliveries, the most recent delivery was included. Maternal characteristics are presented by use of ASA. The accuracy of the ASA prophylaxis use variable in the BORN database was compared to that in the SMH EMR, expressed as sensitivity, specificity, positive (PPV) and negative predictive values (NPV), Cohen’s kappa (κ), and overall percent agreement, with 95% confidence intervals (CI). Sensitivity analyses were performed to account for missing or unclear ASA prophylaxis use.

Results: Among 200 women with a livebirth, 24 (12.0%) had ASA prophylaxis for PE, using BORN and EMR databases. Women using ASA were older (37.0 vs 33.0 years) and had higher median gravidity (3.0 vs. 2.0). Sensitivity and specificity of the BORN ASA prophylaxis variable were 62.5% (95% CI 40.6, 81.2) and 100.0% (95% CI 97.3, 100.0), respectively. The corresponding PPV was 100.0% (95% CI 78.2, 100.0) and NPV 93.8% (95% CI 88.6, 97.1). Cohen’s κ was 0.74 (95% CI 0.58, 0.90), and overall percent agreement 94.4% (95% CI 87.1, 100.0).

Conclusions: Based on the high specificity and modest sensitivity, this study suggests that the ASA prophylaxis variable is validly collected within the BORN administrative health database. Data about the timing of ASA initiation, or its duration of use, have yet to be validated.