Comparison of Lamellar Body Counts Using Light Microscopy with Standard Coulter Counter Techniques to Assess Fetal Lung Maturity

Abstract

Objective: To determine if lamellar body counts determined using light microscopy and a manual hemochromocytometer correlate with counts made on standard electronic cell counters. Methods: Aliquots of amniotic fluid samples obtained by amniocentesis to assess fetal lung maturity were divided into two sterile tubes. One tube was sent immediately to be counted in a cell counter by standard technique and the other tube was stored at –70°C until manual counting could be performed. Manual counts on the same samples were made on two different occasions. Intra-observer variability and correlation with the standard technique was determined. Pearson coefficient was calculated. Results: There were 11 specimen pairs. The intra-observer correlation was significant: intraclass correlation coefficient 0.95 (CI 0.84–0.99). There was significant correlation between the Coulter counter lamellar body counts and manual counts: intraclass correlation coefficients 0.88 (CI 0.62–0.97) and 0.92 (CI 0.73–0.98), respectively. Conclusion: Lamellar body counts determined by light microscopy correlate well with results obtained for lamellar body counts using standard Coulter counter techniques. Results of this pilot study show that this experimental method of evaluating fetal lung maturity deserves further evaluation.