RACIAL-DIFFERENCES IN THE PREDICTIVE VALUE OF THE TDX FETAL LUNG MATURITY ASSAY

OBJECTIVE: Black newborns have lower rates of neonatal respiratory dis tress syndrome compared with nonblack newborns. This has been attribut ed to accelerated lung maturation. Previous studies have demonstrated a difference in the predictive value of the lecithin/sphingomyelin rat io, a test for lung maturity, between races. Our study examines the pr edictive value of the newer TDx Fetal Lung Maturity Surfactant-to-Albu min assay. STUDY DESIGN: We reviewed the records of 393 nonblack and 8 7 black infants delivered within 72 hours of the TDx FLM S/A assay tes ting. We compared the rates of neonatal respiratory distress syndrome by race, stratified by results. RESULTS: In our study population black newborns had less than one half the rate of respiratory distress synd rome compared with nonblack newborns (4.6% vs 10.4%). To adjust for po ssible differences in the timing of lung maturation, the results were stratified by the TDx FLM S/A assay result. Black race had a protectiv e effect (Mantel-Haenszel weighted odds ratio 0.30, 95% confidence int erval 0.06 to 0.93, p < 0.05). This significant racial difference rema ined when both TDx FLM S/A assay result and gestational age were contr olled in a multiple logistic regression analysis. CONCLUSIONS: There a re differences in the predictive value of the TDx FLM S/A assay among races. Black fetuses are less likely to have respiratory distress synd rome. The difference in rates of respiratory distress syndrome between races must be due to either a qualitative difference in the surfactan t or to an anatomic difference in fetal lungs. Consideration should be given to a lower cutoff value for a mature test result in black women .