Lamellar body counts in amniotic fluid for prediction of fetal lung maturity

Objective: Comparison of three different methods of fetal lung maturity (FL M) testing in amniotic fluid (AF) to predict fetal respiratory distress syn drome (RDS): phospholipid concentration, phosphatidylglycerol (PG) and lame llar body count (LBC). Study design: 315 amniotic fluid (AF) samples were t ested, 291 by determination of phospholipid, 237 by PG and 68 by LBC. Eight y one patients (26%) delivered within 3 days, incidence of RDS was 7% (n=6) . Correlation of phospholipids and LBC to gestational age was analyzed as w ell as correlation of LBC and PG versus phospholipid concentration. Sensiti vity and specificity for all three methods were calculated. Results: Phosph olipids and LBC increased exponentially with gestational age (r(regr)=0.54, p<0.01, r(regr)=0.76, p<0.01) showing a curvilinear function. There was a linear correlation between both methods (r(corr)=0.51, p<0.02, n=47). Sensi tivity for prediction of RDS was 80% for phospholipids compared to 83% for LBC and 67% for PG. Specificity was best for PG (92%) followed by phospholi pids (85%). While positive predictive value was low (27% for phospholipids and 50% for LBC), negative predictive value varied between 97% and 100%. Co nclusion. LBC is a simple and reliable method for FLM testing, with a sensi tivity comparable to phospholipid testing and a somewhat lower specificity (67% vs. 85%). It may be useful for screening of FLM in a cascade approach.