POPULATION DIFFERENCES AFFECT THE INTERPRETATION OF FETAL NONSTRESS TEST-RESULTS

OBJECTIVE: The object of the study was to determine whether population differences exist with respect to outcomes of women with reactive and nonreactive nonstress test results. STUDY DESIGN: An epidemiologic ev aluation was conducted on 2579 women who underwent nonstress tests in the Fetal Assessment Center of the Johns Hopkins Hospital within a wee k of delivery. Risk factors such as hypertension, diabetes, and postte rm pregnancy were used in a logistic regression model to evaluate the ability of the nonstress test to predict outcomes including proxies of fetal distress and fetal and neonatal death. The sensitivities, speci ficities, and predictive values of the nonstress test for predicting t hese outcomes in cohorts of black and white women were also determined . RESULTS: The nonstress test was consistently more sensitive for blac k women than for white women in predicting several perinatal outcomes, but specificity and negative predictive value were consistently lower for black women. The positive predictive value for fetal and neonatal death was higher for white women than for black women. Although the n onreactive nonstress test result seemed to be predictive of certain pe rinatal events, the odds ratio for predicting perinatal mortality in a ny study population was no greater than when the nonstress test result was reassuring. CONCLUSIONS: Epidemiologic characteristics affecting test results, such as disease prevalence and population differences, m ay lead to clinically significant differences in outcome prediction wh en these tests' results are used. These differences should be consider ed in the implementation of antepartum fetal testing programs.