title: Lecithin/sphingomyelin ratio and lamellar body count. What values predict the presence of phosphatidylglycerol?
abstract: OBJECTIVE
  To assess which values of the lecithin/sphingomyelin (L/S) ratio and lamellar body count (LBC) optimally correspond to the presence of phosphatidylglycerol (PG).
  
  
  METHODS
  A database of clear amniotic fluid specimens obtained by amniocentesis was accessed. Receiver operating characteristic curve analysis was performed for both L/S ratio and LBC to identify the optimal thresholds for predicting the presence of PG.
  
  
  RESULTS
  One hundred eighty-eight patients were included in the analysis. "Trace" PG was more like "absent" PG in relation to both L/S ratio and LBC. There were significant relationships between L/S ratios and presence of PG (area under the curve = .909, P < .0001) and between LBC and presence of PG (area under the curve = .94, P < .0001). The positive predictive value of L/S ratio > 2 was 76%, and that of LBC > 30,000 was 82% in predicting the presence of PG. Optimal threshold values for the prediction of PG presence were > 3.0 for L/S ratio, which had a positive predictive value of 95% and false positive rate of 5%, and > 50,000 for LBC, with a 96% positive predictive value and 5% false positive rate.
  
  
  CONCLUSIONS
  "Mature" results for PG in amniotic fluid are equivalent to an L/S ratio of > 3.0 and LBC > 50,000 and help explain the later gestational age at the appearance of lung maturity by PG than by L/S > 2 or LBC > 30,000.
authors.affiliation: Departments of Obstetrics and Gynecology and of Pharmacology, Georgetown University Hospital, Washington, D.C., USA. shp2@gunet.georgetown.edu
authors.forename: Sarah H
authors.initials: SH
authors.lastname: Poggi
authors.forename: Catherine Y
authors.initials: CY
authors.lastname: Spong
authors.forename: John C
authors.initials: JC
authors.lastname: Pezzullo
authors.forename: Patricia Z
authors.initials: PZ
authors.lastname: Bannon
authors.forename: Katie M
authors.initials: KM
authors.lastname: Goodwin
authors.forename: Joy
authors.initials: J
authors.lastname: Vink
authors.forename: Alessandro
authors.initials: A
authors.lastname: Ghidini
mesh_terms: D000328:Adult; D000653:Amniotic Fluid / Q000737:chemistry / Q000166:cytology; D005314:Embryonic and Fetal Development; D005260:Female; D005865:Gestational Age; D006801:Humans; D008168:Lung / Q000166:cytology / Q000196:embryology*; D010713:Phosphatidylcholines / Q000032:analysis*; D010715:Phosphatidylglycerols / Q000032:analysis*; D011237:Predictive Value of Tests; D011247:Pregnancy; D013109:Sphingomyelins / Q000032:analysis*
chemical_list: D010713:Phosphatidylcholines; D010715:Phosphatidylglycerols; D013109:Sphingomyelins