Determining a cutoff for fetal lung maturity with lamellar body count testing.
OBJECTIVE
A lamellar body count (LBC) >or= 50,000/microl is suggested to document fetal lung maturity (FLM). We sought to determine the LBC threshold for FLM with the Cell-dyn 4000 hematology analyser.


METHODS
We queried our database for patients who underwent LBC testing from 2001 to 2007. Included were deliveries between 35 and 38 weeks gestation with testing <or=7 days from delivery. We excluded twins, anomalies and cases of ruptured membranes. Data were analysed for sensitivity and specificity of predicting respiratory distress syndrome (RDS) and plotted on a receiver operating characteristic curve.


RESULTS
There were 209 patients meeting study criteria. Of these, 120 had diabetes. Five neonates experienced RDS, all born to non-diabetic mothers with LBC values <or=72,000/microl. At this value the sensitivity is 100%, false positive rate 18% and the p value is 0.0146.


CONCLUSIONS
Our results question the 50,000/microl threshold and demonstrate the need for hematology analyser specific thresholds.
Janicki
Mary Beth
MB
Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Saint Francis Hospital and Medical Center, Hartford, Connecticut 06105, USA.
Dries
Lisa M
LM
Egan
James F X
JF
Zelop
Carolyn M
CM
D000293:Adolescent; D000328:Adult; D000649:Amniocentesis / Q000379:methods / Q000592:standards; D005260:Female; D005325:Fetal Organ Maturity / Q000502:physiology*; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D008168:Lung / Q000196:embryology*; D008875:Middle Aged; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods / Q000592:standards*; D011379:Prognosis; D012372:ROC Curve; D012016:Reference Values; D012680:Sensitivity and Specificity; D055815:Young Adult