Prediction markers for respiratory distress syndrome: evaluation of the stable microbubble test, surfactant protein-A and hepatocyte growth factor levels in amniotic fluid.

Surfactant treatment in infants with respiratory distress syndrome (RDS) has decreased neonatal mortality. With the advent of this therapy, it has become important to predict accurately the fetal lung maturity of a fetus before delivery. We evaluated the stable microbubble test (SMT), surfactant protein-A (SP-A) and hepatocyte growth factor (HGF) in amniotic fluid as predicting markers for RDS. Of 55 amniotic fluid samples obtained by amniocentesis from women less than 37 weeks pregnant, the SMT values were as follows: sensitivity 76.5%, specificity 84.2%, positive predictive value 68.4%, negative predictive value 88.9% and overall accuracy 81.8%. For SP-A, the values were 88.2%, 65.8%, 53.6%, 92.6% and 72.7%, respectively. If we used both SMT and SP-A, we could diagnose with 100% accuracy that a case with measurements of SMT > or = 2 and SP-A > or = 420 ng/ml would not complicate with RDS (24/24). However, the RDS diagnostic accuracy of HGF does not equal to those of SMT and SP-A levels. We concluded that the rapidity, simplicity and reliability of SMT was very useful during 24-36 weeks of gestation as a bedside procedure to predict fetuses likely to develop RDS. We also noted the additive effect of SP-A in improving the accuracy of lung maturity diagnosis.