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

Comparison of three different methods of fetal lung maturity (FLM) testing in amniotic fluid (AF) to predict fetal respiratory distress syndrome (RDS): phospholipid concentration, phosphatidylglycerol (PG) and lamellar body count (LBC).

315 amniotic fluid (AF) samples were tested, 291 by determination of phospholipid, 237 by PG and 68 by LBC. Eighty 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 well as correlation of LBC and PG versus phospholipid concentration. Sensitivity and specificity for all three methods were calculated.

Phospholipids and LBC increased exponentially with gestational age (rregr = 0.54, p < 0.01, rregr = 0.76, p < 0.01) showing a curvilinear function. There was a linear correlation between both methods (rcorr = 0.51, p < 0.01, n = 47). Sensitivity 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 phospholipids (85%). While positive predictive value was low (27% for phospholipids and 50% for LBC), negative predictive value varied between 97% and 100%.

LBC is a simple and reliable method for FLM testing, with a sensitivity comparable to phospholipid testing and a somewhat lower specificity (67% vs. 85%). It may be useful for screening of FLM in a cascade approach.