Interpretation of the TDx-FLM fluorescence polarization assay in pregnancies complicated by diabetes mellitus

The mean weekly increment of amniotic fluid TDx-FLM II ratio is constant during the latter part of pregnancy

OBJECTIVE

The purpose of this study was to determine the mean weekly increment in amniotic fluid TDx-FLM II ratio during the latter part of pregnancy.

STUDY DESIGN

All women who underwent > 1 amniocentesis for the determination of fetal lung maturity between 1998 and 2004 were identified retrospectively. Clinical information and TDx-FLM II ratios were collected from the participant's chart and analyzed.

RESULTS

The gestational age of all participants at the first TDx-FLM II test was 31.2 to 37.5 weeks (mean, 34.7 +/- 1.4 weeks of gestation). The median interval between the 2 tests was 7 days (range, 5-36 days). We found that the mean weekly increment of TDx-FLM II was 14.4 +/- 9.9 mg/g (surfactant to albumin) and remained constant across the gestational ages.

CONCLUSION

The mean weekly increment of TDx-FLM II is 14.4 +/- 9.9 mg/g and is constant during the latter part of pregnancy. This information, combined with the gestational age, should be useful in treating women with an initial immature test.

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.