Amniotic fluid surfactant-albumin ratio as a screening test for fetal lung maturity. Two years of clinical experience
Bayer-Zwirello, L.A.; Jertson, J.; Rosenbaum, J.; Moccio, R.; O'Grady, J.P.; Kanaan, C.M.; Gimovsky, M.L.
Journal of perinatology official journal of the California Perinatal Association 13(5): 354-360
1993
ISSN/ISBN: 0743-8346 PMID: 8263619 Document Number: 418021
An automated amniotic fluid surfactant-albumin ratio (SAR) test was performed as a screening test for pregnancies requiring fetal pulmonary maturity testing. Of the 178 neonates delivered within 3 days of the testing, respiratory distress syndrome (RDS) developed in 21 (11.8%) and transient tachypnea of the newborn infant (TTN) in 11 (6.1%). A positive test was defined as one which predicted RDS or TTN. Sensitivity was interpreted as the proportion of neonates with RDS or TTN detected by SAR less than 70 mg/gm. Sensitivity was 90.7% with a specificity of 76.1%. The positive predictive value was 45.3%; the negative predictive value 97.4%. The interassay coefficient of variability was 3.5%. The SAR test has proven to be a rapid, precise laboratory tool. Our combined testing protocol uses the SAR as an initial screening test with the lecithin/sphingomyelin ratio used as backup if the SAR did not predict maturity (SAR < 70 mg/gm). This protocol has markedly lowered the use of lecithin/sphingomyelin ratios while maintaining necessary clinical accuracy.