[Assessment of fetal lung maturity using newly developed immunological measurement of fetal pulmonary surfactant apoprotein-A in amniotic fluid].

The level of immunoreactive lung surfactant apoprotein A (SP-A) was determined with a newly developed one-step ELISA kit (TDR-20) in 217 samples obtained by transabdominal or transvaginal amniocentesis from 217 pregnant women with high risk pregnancy. The lecithin/sphingomyelin ratio (L/S ratio) by two-dimensional thin layer chromatography, disaturated phosphatidylcholine (DSPC) values, shake test and the stable microbubble method were done simultaneously to compare diagnostic reliability in estimating fetal lung maturity. Amniotic fluid SP-A levels increased with advancing gestational age and correlated well with the values obtained by the other methods. When the cut-off SP-A value for the assessment of lung maturity was set at 1,700ng/ml in the amniotic fluid obtained within 24h before delivery, the true-negative rate for RDS was 71% and the true-positive rate for non-RDS was 83%. The sensitivity, specificity and accuracy were 100%, 83% and 88%, respectively. These results are comparable with those for the L/S ratio, DSPC determination and the stable microbubble method, and were slightly better than those for the shake test. In conclusion, this newly developed ELISA kit for the measurement of amniotic fluid SP-A is more effective than other methods currently available for the evaluation of fetal lung maturity, when it is considered that it requires only 0.2ml of amniotic fluid and provides results in only 2h without technical difficulties.