The tap test: confirmation of a simple, rapid, inexpensive, and reliable indicator of fetal pulmonary maturity.

The tap test was previously described, and preliminary experience suggested it might be a rapid, inexpensive, and reliable indicator of fetal lung maturity. In this expanded series of 332 patients delivered of infants within 72 hours of amniotic fluid analysis, the predictive values for mature test results at 2, 5, and 10 minutes were 98.9% (182 of 184), 97.4% (221 of 227), and 97.1% (233 of 240), respectively. Predictive values for immature test results were 41.2% (61 of 148), 54.3% (57 of 105), and 60.9% (56 of 92). For the phospholipid profile the predictive value was 96.9% (186 of 192) for a mature test result and 40.7% (57 of 140) for an immature result. These observations, coupled with its methodologic simplicity, make the tap test a good first step in a cascade scheme of tests for fetal lung maturity and a valuable test in a facility where the phospholipid profile is not available 24 hours a day.