Amniotic fluid lamellar body count as a cost-effective screening test for fetal lung maturity

OBJECTIVE: To describe lamellar body counts (LBC) in unspun amniotic fluid specimens and to create a highly specific cascade testing scheme for fetal lung maturity (FLM) using LBC, I,:S and PC. METHODS: We analyzed amniotic fluid samples on 203 patients undergoing maturity amniocentesis. L:S and PG were performed using thin layer chromatography. LBC was measured on the platelet channel of a hematology analyzer (Sysmex NE1500) in duplicate. Maximally specific LBC cutoffs for mature and immature L:S and PG values were determined using receiver operator curves. RESULTS: No technical difficulties with the analyzer were encountered. The interassay variability was 1.3. L:S MATURE PC MATURE L:S&PG IMMATURE LBC > 32,000 > 100,000 <8,000 SPECIFICITY 100% 99% 100% CONCLUSION: Testing only specimens where 8,000 < LBC and <32,000 for PG and L:S would preclude the need for 77% of all PG and L:S assays in our population. The cosl, availability and time required to run a LBC is the same as that for a CBC. This is in contrast to the expensive, time-consuming, and often unavailable PG and L:S assays. The exact savings per patient with a diagnostic LBC would be S122. With our large sample size we confidently propose a cascade scheme for FLM using the LBC. This is the first report of LBC using tinspun amniotic fluid.