Bubble stability test compared with lecithin assay in prediction of respiratory distress syndrome

A simple test for surfactant, utilizing bubble stability in ethanol, was performed in 106 samples of amniotic fluid obtained from 94 patients. Of these patients 80 delivered within 48 hours of the collection of the sample. The results were compared with the lecithin concentration in the same amniotic fluid samples and with the quality of respiration in the neonate. The test was "positive," indicating fetal pulmonary maturity, in 37 cases and none of these infants developed respiratory distress syndrome (R.D.S.). In only one of these cases, however, was gestation less than 37 weeks. The test was "intermediate" or "negative" in 43 cases but in 35 of these infants respiration at birth was perfectly normal.Performed by the method described by its originators, this simple test gives too many false negative results to be of value in routine clinical practice, although a positive result is helpful. The concept of the test is ingenious, however, and further developments may be expected.