Prediction of fetal lung maturity by use of the Lumadex-FSI test.

We analyzed amniotic fluid from 91 pregnancies (estimated gestational age range 31 to 41 weeks), using the Lumadex-FSI Fetal Lung Maturity test (Beckman Instruments), and also determining phosphatidylglycerol content, the lecithin/sphingomyelin ratio, and foam stability index by the "shake test," and compared results with newborn outcome. Five of 64 babies born within 72 h of testing developed hyaline membrane disease. Except for the lecithin/sphingomyelin ratio, the predictive value of a negative test was 100% but that of a positive test was less than 50%. Use of all four tests did not offer diagnostic advantage over the use of Lumadex-FSI alone. For the laboratory that infrequently assesses fetal lung maturity, we believe the sealed cassette format of the Lumadex-FSI will permit better quality assurance than the shake test. The Lumadex-FSI test is intended to provide a graded estimate of positive risk for hyaline membrane disease, but more data from different centers and patient populations are needed to establish reliable predictive values.