RESUMO
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.
