The effects of vaginal contamination on two pulmonary phospholipid assays

During the examination to confirm premature rupture of membranes, amniotic fluid unavoidably contaminated with cervical mucus and other vaginal debris can often be obtained from the posterior fornix. This study was undertaken to determine the validity of phospholipid measurements on contaminated amniotic fluid. Fifteen paired amniocentesis and vaginally contaminated samples of amniotic fluid were used to measure the lecithin/sphingomyelin ratio and saturated phosphatidylcholine (SPC). The amniocentesis specimens had a mean L/S ratio of 3.94 +/- 0.22 (mean +/- SEM), and contaminated samples had a mean L/S ratio of 3.82 +/- 0.29 (mean +/- SEM). Paired t-test was unable to demonstrate a significant difference (p greater than 0.10), and the correlation coefficient between paired L/S samples was r = 0.79. SPC measurements on the amniocentesis fluid had a mean value of 1,243 microgram/DL +/- 217 (mean +/- SEM) as compared to the contaminated-specimen mean of 1.375 micrograms/dl 223 (mean +/- SEM). Paired t-test likewise was unable to demonstrate a significant difference (p greater than 0.10), and the correlation coefficient between paired SPC samples was r = 0.93. Within the design of this study, we were unable to demonstrate a statistically significant effect of brief vaginal contamination on the measurement of the L/S ratio or SPC.