Amniotic fluid polarization of fluorescence and lecithin/sphingomyelin ratio decision criteria assessed.

A negative finding of amniotic fluid (AF) phosphatidyl glycerol (PG) does not eliminate the need for determining the lecithin/sphingomyelin ratio (LSR). We use a novel approach to classify fetal lung maturity (FLM) data, and to validate the fluorescence polarization (FP) surfactant assay (Abbott), which replaces the PG assay and reduces the frequency of repeat LSR. This method finds the values (decision points) of these tests that allow for classifying the data with least errors. These tests best identify the risk of respiratory distress syndrome (RDS) from fetal lung immaturity. We find the decision values for tests by exploring the data for information content and optimize their selection using group-based reference. We previously defined normal reference as the maximum entropy set with no information. The uncertainty resolved by information provided in the data allows formation of syndromic classes. This is greatest at the values for the variables (decision-points) associated with the greatest decrease in entropy. Decision-values found for PF, EGA, PG, LSR that classify amniotic fluids into the mature and not-mature classes are in agreement with the results of ROC analysis. We validate the replacement of PG by the PF method. We also find a level of FP below which LSR might be required to resolve uncertainty and above which the FP indicates maturity. We confirm the ability to evaluate fetal maturity methods using information analysis.