Lamellar body counts compared with traditional phospholipid analysis as anassay for evaluating fetal lung maturity

Objective: To compare lamellar body counts with the lecithin/sphingomyelin ratio and phosphatidylglycerol analysis in terms of assessment of risk of r espiratory distress syndrome (RDS). Methods: Lamellar body counts, lecithin-sphingomyelin ratios (L/Ss), and ph osphatidylglycerol levels were assessed in 1611 amniotic fluid samples obta ined at four clinical sites from pregnant women whose fetuses were at risk for RDS. Cases in which delivery occurred within 72 hours of sample collect ion (n = 833) were analyzed. Specific cutoffs for predicting the likelihood of RDS for both the lamellar body count and the LIS had been derived previ ously at each of the clinical sites based on receiver operating characteris tic curves using unrelated samples, whereas phosphatidylglycerol was report ed as either mature (present) or immature (absent). Standard clinical and r adiographic criteria were used to diagnose RDS, and the diagnosis was confi rmed by review of newborn records. Results: One hundred (12.0%) of the 833 infants delivered within 72 hours o f sample collection developed RDS. The negative predictive value of the lam ellar body count (97.7%) was similar to that of the CIS (96.8%) and slightl y better than that of phosphatidylglycerol analysis (94.7%) (P =.048). The lamellar body count performed as well as phospholipid analysis irrespective of gestational age or patient population. Conclusion: The lamellar body count compares favorably with traditional pho spholipid analysis as an assay for assessment of fetal lung maturity. Lamel lar body counts are preferable because they are faster, more objective, les s labor intensive, less technique dependent, and less expensive and because they can be performed with equipment available in every hospital laborator y. (Obstet Gynecol 2001;97;305-9. (C) 2001 by The American College of Obste tricians and Gynecologists.).