The usefulness of the TDx/TDxFLx fetal lung maturity II assay in the initial evaluation of fetal lung maturity

Objective: This study was undertaken to evaluate the usefulness of the TDx/TDxFLx Fetal Lung Maturity II (FLM II) assay (Abbot Laboratories, Abbot Park, Ill) in the initial evaluation of fetal lung maturity. Study Design: One hundred twenty-seven women who underwent amniotic fluid collection through amniocentesis or vaginal pool for fetal lung maturity studies were evaluated for inclusion. The uncontaminated amniotic fluid specimens were analyzed within 24 hours with the use of the TDx/TDxFLx FLM II assay with values 55 mg/g or greater considered mature, values between 40 and 54 mg/g considered intermediate, and values 39 mg/g or less considered immature. Eighty-two women with singleton gestations who were delivered within 72 hours were included in the final analysis. We compared the TDX/TDxFLx FLM II test with the presence of neonatal respiratory distress syndrome (RDS). Results: Seven of the 82 (8.5%) neonates had RDS develop. None of the 60 neonates with mature values had RDS develop. Two of 10 (20%) neonates with intermediate values and 5 of 12 (42%) neonates with immature values had RDS develop. With the use of a cutoff value of 55 mg/g, the TDx/TDxFLx FLM II assay had sensitivity and a negative predictive value of 100%, a specificity of 80%, and a positive predictive value of 31.8%. Conclusion: The TDx/TDxFLx FLM II assay is a useful tool in determining fetal lung maturity by using a cutoff value of 55 mg/g. (Am J Obstet Gynecol 2003;188:1220-2.)