Comparison of the Lumadex-foam stability index test, lecithin: sphingomyelin ratio, and simple shake test for fetal lung maturity.

Amniotic fluid was obtained from 269 patients within 72 hours of delivery. The sensitivity, specificity, and predictive value of the Lumadex-foam stability index test, lecithin: sphingomyelin (L:S) ratio, and simple shake test were assessed in the diagnosis of respiratory distress syndrome (RDS), as well as the accuracy in identification of functional lung maturity in the growth-retarded fetus. The Lumadex-foam stability index test was found to be an accurate, quantitative, simple, and rapid measure of fetal lung maturity in the normal as well as abnormal pregnancy. The L:S ratio was accurate in the normal pregnancy, but became inaccurate in the small growth-retarded fetus. The nonquantitative simple shake test was accurate when it indicated fetal lung maturity, but an immature result was meaningless because of the large false-negative rate.