The tap test--an accurate first-line test for fetal lung maturity testing.

ABSTRACT

OBJECTIVE: To determine the accuracy of near-patient and laboratory-based fetal lung maturity tests in predicting the need for neonatal ventilation. DESIGN: A prospective descriptive study. SUBJECTS: One hundred high-risk obstetric patients where confirmation of fetal lung maturity would initiate delivery. METHODS: Fetal weight estimation, placental maturity grading, and amniocentesis were performed. The investigators examined the amniotic fluid visually, and performed the tap test and shake test. Laboratory technicians estimated the lecithin-sphingomyelin (L/S) ratio, determined the presence of a phosphatidyl glycerol (PG) band on gel electrophoresis, and the optical density at 650 nm. Neonates delivered within 1 week of amniocentesis were included in the analysis. The primary end-point was the ability of the lung maturity tests to predict the need for neonatal ventilation. RESULTS: Twelve of 100 neonates required ventilation. The tap test and optical density (OD) shift at 650 nm predicted the need for neonatal ventilation with the greatest accuracy. CONCLUSION: The tap test is a rapid, easy and accurate predictor of the need for neonatal ventilation. The OD shift at 650 nm is the laboratory-based test with the greatest accuracy in our setting.