A COMPARISON OF RAPID AMNIOTIC-FLUID MARKERS IN THE PREDICTION OF MICROBIAL INVASION OF THE UTERINE CAVITY AND PRETERM DELIVERY

OBJECTIVE: The purpose of this study was to evaluate amniotic fluid la ctate dehydrogenase level in comparison with other rapid markers in pr ediction of microbial invasion of the uterine cavity and preterm deliv ery less than or equal to 36 hours after amniocentesis. STUDY DESIGN: One hundred thirty-one women in preterm labor with intact membranes un derwent transabdominal amniocentesis. Amniotic fluid was analyzed for leukocyte count, glucose level, lactate dehydrogenase level, and Gram stain. Cultures for aerobes, anaerobes, and Mycoplasma sp, were perfor med. Amniocentesis-to-delivery interval was calculated. The study grou p was divided and the findings compared according to amniotic fluid cu lture results and according to amniocentesis-to-delivery interval. Sen sitivity, specificity and positive and negative predictive value were calculated for lactate dehydrogenase, leukocyte count, glucose, and Gr am stain in the prediction of positive amniotic fluid culture and pret erm delivery less than or equal to 36 hours after amniocentesis. Recei ver-operator characteristic curve analysis, logistic regression analys is, t tests, and nonparametric tests were used. RESULTS: The prevalenc e of positive amniotic fluid cultures was 12% (16 of 131). The median lactate dehydrogenase level (1084 U/L) was significantly greater for w omen with a positive amniotic fluid culture than for those with a nega tive culture (median lactate dehydrogenase level 194 U/L; p < 0.0002). The critical values calculated for optimal performance in prediction of a positive amniotic fluid culture were a lactate dehydrogenase leve l greater than or equal to 419 U/L, leukocyte count greater than or eq ual to 50 cells/mm(3) (50 x 10(6)/L) and glucose less than or equal to 17 mg/dl (0.94 mmol/L). Lactate dehydrogenase, leukocyte count, gluco se, and Gram stain were equally sensitive and specific in prediction o f a positive amniotic fluid culture. Thirty-nine women (29.8%) gave bi rth less than or equal to 36 hours after amniocentesis. The median lac tate dehydrogenase level (414 U/L) was significantly greater among wom en giving birth less than or equal to 36 hours after amniocentesis tha n among women giving birth less than or equal to 36 hours after amnioc entesis (median lactate dehydrogenase, 173 U/L; p < 0.001). Critical v alues of lactate dehydrogenase greater than or equal to 225 U/L, leuko cyte count greater than or equal to 10 cells/mm3 (1 0 x 106/L) and glu cose less than or equal to 34 mg/dl (1.9 mmol/L) were selected for opt imal performance in prediction of amniocentesis-to-delivery interval l ess than or equal to 36 hours. Lactate dehydrogenase level had the bes t sensitivity (74%) in prediction of delivery less than or equal to 36 hours after amniocentesis in contrast to leukocyte count (49%), gluco se (62%), and positive Gram stain (26%). Amniotic fluid lactate dehydr ogenase values greater than or equal to 225 U/L were associated with a fivefold greater risk for delivery less than or equal to 36 hours aft er amniocentesis (odds ratio 5.46, 95% confidence interval 2.00 to 14. 87; p = 0.0006). CONCLUSION: Amniotic fluid lactate dehydrogenase leve l has diagnostic value in prediction of a positive amniotic fluid cult ure and delivery less than or equal to 36 hours after amniocentesis. L actate dehydrogenase is a readily available, inexpensive, rapid amniot ic fluid marker that can be measured in any hospital laboratory.