Lamellar body count in amniotic fluid for assessing fetal lung maturity

Abstract

Respiratory distress syndrome (RDS) of the newborn infant caused by immaturity of fetal lung is a very serious clinical problem. Surfactant is stored in the form of lamellar bodies. They are secreted into alveolar space and passed into amniotic fluid where they can be found. The similarity of lamellar body size to platelet size permits the use of a standard automated hematologic cell counter to estimate the number of lamellar bodies in amniotic fluid. We conducted a prospective clinical study from 2005-2006 on amniotic fluid samples. Amniotic fluid samples were collected near delivery by transvaginal amniotomy, amniotomy during Cesarean section and 72 hours before delivery by amniocentesis. A hematology analyzer (Nikon-Kohden) was used to determine the lamellar body counts. After birth of newborns we compared their complete clinical examination results particularly emphasizing the prediction of the method of RDS by lamellar body count. Maximally specific lamellar body cutoffs for maturity and immaturity were determined using ROC curves. Of 232 amniotic fluid samples which were tested, 112 samples were collected by transvaginal amniotomy, 88 were taken during Cesarean delivery and 32 samples were collected by amniocentesis. The incidence of RDS was 14.6%. ROC curves were used to identify cut points for the test. We found that LBC is a good screening test for predicting fetal lung maturity with the area under the curve of 0.751. LBC cutoff of 42 x 10(3)/microl, with sensitivity of 82.4% and specificity of 64.6%, proved best for predicting fetal lung maturity. LBC is a good screening test for predicting fetal lung maturity. The advantages of LBC are speed, objectivity, low price, low sample volume required and universal availability.