Identifying cardiovascular severe maternal morbidity in epidemiologic studies

Abstract

BackgroundCardiovascular severe maternal morbidity (CSMM) is rising and has become the leading cause of maternal mortality. Research using administrative data sets may allow for better understanding of this critical group of diseases.ObjectiveTo validate a composite variable of CSMM for use in epidemiologic studies.MethodsWe analysed delivery hospitalisations at an obstetric teaching hospital from 2007 to 2017. We utilised a subset of indicators developed by the Centers for Disease Control and Prevention based on ICD codes to form the composite variable for CSMM. Two expert clinicians manually reviewed all qualifying events using a standardised tool to determine whether these represented true CSMM events. Additionally, we estimated the number of CSMM cases among delivery hospitalisations without qualifying ICD codes by manually reviewing all hospitalisations with severe preeclampsia, a population at high risk of CSMM, and a random sample of 1000 hospitalisations without severe preeclampsia. We estimated validity of the composite variable.ResultsAmong 91 355 admissions for delivery, we captured 113 potential CSMM cases using qualifying ICD codes. Of these, 65 (57.5%) were true CSMM cases. Indicators for acute myocardial infarction, cardiac arrest, and cardioversion had the highest true‐positive rates (100% for all). We found an additional 70 CSMM cases in the 2102 admissions with severe preeclampsia and a single CSMM case in the random sample. Assuming a rate of 1 CSMM case per 1000 deliveries in the remaining cohort, the composite variable had a positive predictive value of 57.5% (95% CI 47,9, 66.8), a negative predictive value of 99.8% (95% CI 99.8, 99.9), a sensitivity of 29.0% (95% CI 23.2, 35.4), and a specificity of 100% (95% CI 99.9, 100.0).ConclusionA novel composite variable for CSMM had reasonable PPV but limited sensitivity. This composite variable may enable epidemiologic studies geared towards reducing maternal morbidity and mortality.

Cardiovascular severe maternal morbidity in pregnant and postpartum women: development and internal validation of risk prediction models

“…A comprehensive combination of ICD codes was used to identify women with the outcome of interest. Moreover, each outcome was manually verified by clinicians using a standardised instrument 16 . The models had strong discrimination ability.…”

“…Even though we reviewed the medical records of women with relevant ICD codes, some CSMM events may have been misclassified as non‐events in the total cohort. We previously estimated the rate of misclassified CSMM at delivery to be close to 1 CSMM (95% CI 0–6) per 1000 deliveries 16 . The rate of missed postpartum CSMM events remains unknown.…”

“…Their medical records were manually reviewed by two clinicians to confirm the presence of true CSMM events (IM and NM). The clinicians used a standardised data abstraction instrument described in detail elsewhere and previously found to have excellent inter‐observer reliability 16 . In brief, CSMM events had to be provoked or exacerbated by pregnancy and diagnostic confirmation had to be documented by at least one method (including clinical examination, laboratory or radiological testing, expert consultation or response to therapy).…”

“…Moreover, each outcome was manually verified by clinicians using a standardised instrument. 16 The models had strong discrimination ability. Although several tools may be used to estimate the risk of cardiovascular morbidity among pregnant women with known cardiac Beta coefficients and odds ratios represent the differences in log odds differences or ratios of odds ratios for each variable included in the interaction, stratified by the other variable (e.g.…”

“…The clinicians used a standardised data abstraction instrument described in detail elsewhere and previously found to have excellent inter-observer reliability. 16 In brief, CSMM events had to be provoked or exacerbated by pregnancy and diagnostic confirmation had to be documented by at least one method (including clinical examination, laboratory or radiological testing, expert consultation or response to therapy). For instance, women with congenital heart disease admitted to a critical care unit for monitoring only and clinically stable, were not considered as having CSMM.…”