Lecithin/sphingomyelin ratio and lamellar body count for fetal lung maturity: a meta-analysis

Objective: To determine and compare the diagnostic accuracy of the lecithin/sphingomyelin (L/S) ratio and lamellar body count (LBC) in the prediction of neonatal respiratory distress syndrome (RDS). Study design: A systematic review was performed to identify studies comparing either the L/S ratio or the LBC with the occurrence of RDS published between January 1999 and February 2009. Two independent reviewers performed study selection and data extraction. For each study sensitivity and specificity were calculated. Summary receiver-operating characteristics (ROC) curves, assessing the diagnostic performance of both tests, were constructed. A subgroup analysis was performed to estimate the sensitivity and specificity of the various cut-off values. Results: 13 studies were included. The ROC curves of the collected data illustrate that the LBC and L/S ratio perform equally well in the prediction of RDS. Comparison of the two summary ROC curves of each test indicates that the diagnostic performance of LBC might even have a slight advantage over L/S ratio. Due to the wide cut-off range it was not possible to define specific cut-off values with the best accuracy. Conclusion: We recommend replacing the L/S ratio as gold standard with the lamellar body count since the LBC is easy to perform, rapid, inexpensive, and available to all hospitals 24 h per day.