TDx-FLM Test to Determine the Fetal Lung Maturity

Yoo, Seung Chul; Yang, Jeong In; Byun, Young Ji; Lee, Hee Jong; Kim, Haeng Soo; Oh, Kie Suk; Ryu, Hee Sug

Abstract

OBJECTIVE
Our purpose is to determine the optimal cutoff value for the TDx-FLM assay for predicting fetal lung maturity and its clinical efficiency.
METHODS
We reviewed records of 81 pregnant women (117 fetuses), who had TDx-FLM assay performed from 1996 through 2000 at Ajou University Hospital. All were delivered between 28 and 37 weeks' gestation. Women treated with steroids after fetal lung maturity test were excluded in this study. In neonatal respiratory outcomes, result of fetal lung maturity was defined as neonates who were not affected by respiratory distress syndrome (RDS). All neonates were divided into mature and immature group according to their respiratory outcomes and clinical characteristics of both groups were evaluated. The predictive values for maturity and immaturity were calculated as previously defined.
RESULTS
Among 117 newborns, RDS developed in 8 cases (immature group), and 109 cases were unaffected (mature group). In mature and immature group, mean gestational age was 35.0 weeks and 33.1 weeks (p=0.038), mean fetal birth weight 2313.4 gm and 2036.3 gm respectively (p=0.279). Preterm deliveries were due to preterm labor (32.1% vs 25.0%, p=0.676), premature rupture of membranes (11.9% vs 12.5% p=0.962), preeclamsia (17.4% vs 37.5%, p=0.384), intrauterine growth restriction (11.0% vs 0%, p=0.211), discordant twin (16.5% vs 0%, p=0.212) and other maternal complications (35.8% vs 37.5%, p=0.922) And also, frequencies of twin were 0% vs 64.2% (p<0.001), gestational diabetes 3.7% vs 12.5% (p=0.233), steroid usage 67.0% vs 12.5% (p=0.002), and median TDx-FLM level 59.2 mg/g (range 13.8 - 120.4 mg/g) vs 13.1 mg/g (range 1.20-27.9 mg/g) (p=0.004). The best cutoff point to calculate predictive value for a mature result was >or=24.7 mg/g which gave a sensitivity 93.6%, specificity 87.5%, positive predictive value (PPV) 99.0%, negative predictive value (NPV) 50.0% and efficiency 93.1.
CONCLUSION
The best cutoff value of TDx-FLM levels for assessment of fetal lung maturation was 24.7 mg/g in our study group.