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

Abstract

Objective: To compare lamellar body counts with the lecithin/sphingomyelin ratio and phosphatidylglycerol analysis in terms of assessment of risk of respiratory distress syndrome (RDS). Methods: Lamellar body counts, lecithin-sphingomyelin ratios (L/Ss), and phosphatidylglycerol levels were assessed in 1611 amniotic fluid samples obtained at four clinical sites from pregnant women whose fetuses were at risk for RDS. Cases in which delivery occurred within 72 hours of sample collection ( n = 833) were analyzed. Specific cutoffs for predicting the likelihood of RDS for both the lamellar body count and the L/S had been derived previously at each of the clinical sites based on receiver operating characteristic curves using unrelated samples, whereas phosphatidylglycerol was reported as either mature (present) or immature (absent). Standard clinical and radiographic criteria were used to diagnose RDS, and the diagnosis was confirmed by review of newborn records. Results: One hundred (12.0%) of the 833 infants delivered within 72 hours of sample collection developed RDS. The negative predictive value of the lamellar body count (97.7%) was similar to that of the L/S (96.8%) and slightly 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 phospholipid analysis as an assay for assessment of fetal lung maturity. Lamellar body counts are preferable because they are faster, more objective, less labor intensive, less technique dependent, and less expensive and because they can be performed with equipment available in every hospital laboratory.