Lamellar bodies as a diagnostic test of fetal lung maturity.

OBJECTIVES: To determine the number of lamellar bodies in the amniotic fluid indicating fetal lung maturity and to define the effectiveness of a diagnostic test in a healthy pregnant population. METHODS: The study took place at the Hospital General de Zona #16 Centro Médico Nacional del Instituto Mexicano del Seguro Social. Torreón, Coahuila, México, where 264 pregnant women were followed-up from August 1997 to October 1998. The women presented in labor between 26 and 41 weeks of gestation. Amniotic fluid was obtained during cesarean section or from the vaginal pool and lamellar bodies were counted without prior centrifugation in Cell-Dyn 3000's channel for blood platelets. Results were masked for neonatologists. RESULTS: The prevalence of respiratory distress syndrome (RDS) was found to be 14.9%. At the 8200/microl threshold, sensitivity was: 15.4% (95% CI=5.9-30.5%), specificity: 99.6% (95% CI=97.5-99.9%), positive predictive value (PPV): 85.7, negative predictive value (NPV): 87.1, likelihood ratio for a negative test (LR-): 0.85, and likelihood ratio for a positive test (LR+): 85.7. At the 57 000/microl level, sensitivity was: 92.3% (95% CI=79.1-98.3%), specificity: 70.9% (64.4-76.7%), PPV: 35.6, NPV: 98.1, LR-: 0.11, and LR+: 3.17. When the cut-off point was 79000/microl, sensitivity was: 100.0%, specificity: 43.0% (95% CI=36.5-49.8%), PPV: 23.5, NPV: 100.0, LR+: 34.3, and LR-: less than 0.001. CONCLUSIONS: Counting lamellar bodies is a quick, readily available, and very effective test.