TDx-FLM Test to Determine the Fetal Lung Maturity

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.

목적 : 태아의 폐성숙을 예측하기 위한 TDx-FLM 검사의 적정 기준치와 그 임상적 유용성을 알아본다. 연구 방법 : 1996년부터 2000년 아주대학교병원에서 28주에서 37주에 분만된 산모 중 태아 폐성숙 평가를 위해 복식 양수천자를 통해 TDx-FLM을 시행한 81명 (신생아 117명)을 대상으로 하여 후향적 연구를 하였다. 출생 후 신생아 호흡곤란증후군이 없었던 경우를 폐성숙으로 간주하여, 폐성숙군과 미성숙군의 임상적 특성을 살펴보고, 이들의 산전 TDx-FLM 측정치들을 토대로 태아 폐성숙에 대한 TDx-FLM의 적정 기준치를 조사하였다. 폐성숙 검사 이후 스테로이드를 사용한 경우는 대상에서 제외하였다. 결과 : 117명의 신생아 중 8명 (미성숙군)에서 호흡곤란증후군이 발생하였으며, 108명 (폐성숙군)은 이환되지 않았다. 폐성숙군과 미성숙군의 평균 재태연령은 35.0주, 33.1주였고 (p=0.038) 평균 출생체중은 2313.4 gm, 2036.3 gm (p=0.279) 이었다. 양군에서 조산의 원인은 조기진통 (32.1% vs 25.0%, p=0.676), 조기양막파수 (11.9% vs 12.5%, p=0.962), 전자간증 (17.4% vs 37.5%, p=0.384), 태내 발육지연 (11.0% vs 0%, p=0.211), 쌍태아간 체중불일치 (16.5% vs 0%, p=0.212), 그 외 조기분만이 고려되는 태아나 산모의 상태 (35.8% vs 37.5%, p=0.922) 이었다. 또한 쌍태임신의 빈도는 각각 0%, 64.2% (p<0.001), 임신성 당뇨는 3.7%, 12.5% (p=0.233), 분만 전 스테로이드 치료는 67.0%, 12.5% (p=0.002), TDx-FLM의 정중값은 59.2 mg/g (범위 13.8-120.4 mg/g), 13.1 mg/g (범위 1.20 - 27.9 mg/g) (p=0.004) 이었다. ROC curve를 이용한 cutoff치는 24.7 mg/g이며 민감도는 93.6%, 특이도는 87.5%, 양성예측도는 99.0%, 음성예측도는 50.0%, 효율성은 93.1이었다. 결론 : 본 연구 집단에서 태아의 폐성숙 정도를 예측하는데 있어 적절한 TDx-FLM 검사의 기준치는 24.7mg/g이다.