DIAGNOSTIC POWER OF LECITHIN SPHINGOMYELIN RATIO AND FLUORESCENCE POLARIZATION ASSAYS FOR RESPIRATORY-DISTRESS SYNDROME COMPARED BY RELATIVE OPERATING CHARACTERISTIC CURVES/

Amniotic fluids from 328 patients were analyzed for lecithin/sphingomy elin (L/S) ratio and surfactant/albumin (S/A) ratio by fluorescence po larization. Of this group, 61 neonates showed respiratory distress syn drome (RDS) on delivery within 3 days of testing. We compared the powe r of the L/S and S/A in diagnosing pulmonary maturity, using relative operating characteristic (ROC) curves. The area defined by the ROC cur ve of the S/A test exceeded the area defined by the L/S curve, but thi s difference was not statistically significant. The diagnostic power o f the S/A test appears to be at least equal to that of the standard L/ S test. A review of five cases of RDS in which laboratory tests had su ggested maturity showed that neither the L/S nor the S/A could satisfa ctorily resolve the problem of false interpretations of maturity, part icularly in mothers with diabetes mellitus who underwent cesarean sect ion.