Evaluation of the PG-Numeric assay for semi-automated analysis for phosphatidylglycerol in amniotic fluid

We evaluated the performance of the PG-Numeric (PGN; Isolab, Inc.) enzymatic assay for phosphatidylglycerol (PG) adapted for semi-automated analysis on the Cobas-Bio (Roche) centrifugal analyzer. We evaluated precision, linearity, and potential interference from endogenous glycerol. In addition, we compared the results of the PGN assay with those for two other PG assays. Amniostat-FLM (AFLM; Hana Biologics) and phosphatidylglycerol/sphingomyelin ratio (PG/S), on amniotic fluid samples from 51 patients. Within-run and total CVs for the PGN test (n = 80) were respectively 8.6% and 11.4% for PG at 2.6 mumol/L, and 4.5% and 6.2% at 7.3 mumol/L. The PGN test exhibited no significant deviation from linearity between PG concentrations of 0.4 and 15 mumol/L. Endogenous glycerol up to 500 mumol/L did not affect PGN results significantly. Results of the PGN assay compared favorably with those of the other PG assays for tests of fetal lung maturation. The Cobas-Bio adaptation of the PGN test performed well analytically and clinically, and allowed the determination of PG in less than 1 h.