Amniotic fluid matrix metalloproteinase-9 levels in women with preterm labor and suspected intra-amniotic infection

Objective: To determine the accuracy of amniotic fluid (AF) matrix metallop roteinase-9 measurements for diagnosing intra-amniotic infection in women w ith preterm labor. Methods: We performed amniocenteses in 44 women between 22 and 35 weeks' ge station who presented to our center with preterm labor and clinical suspici on of intraamniotic infection. Each sample was analyzed by glucose measurem ent, Gram stain, and culture for aerobes, anaerobes, and mycoplasmas. We te sted the AF for matrix metalloproteinase-9 using gelatin zymography and a c ommercial enzyme-linked immunosorbent assay (ELISA) system. We calculated a ccuracy and confidence intervals (CIs) for AF matrix metalloproteinase-9, g lucose, and Gram stain for diagnosing intra-amniotic infection, using cultu re as the criterion standard. Results: All patients who had matrix metalloproteinase-9 detectable by ELIS A also demonstrated matrix metalloproteinase-9 by zymography. Six cases of intra-amniotic infection were confirmed by culture (prevalence 14%). The pe rformance statistics of AF matrix metalloproteinase-9 for diagnosing intra- amniotic infection were: sensitivity 83% (95% CI 53, 99), specificity 95% ( 95% CI 88, 99), positive predictive value 71% (95% CI 37, 99), and negative predictive value 97% (95% CI 92, 99). Two women had false-positive results ; one had gram-negative rods on the AF Gram stain and developed clinical si gns and symptoms of chorioamnionitis several hours after amniocentesis and the other had a purulent vaginal discharge and an AF glucose level less tha n 15 mg/dL. Both delivered within 24 hours of amniocentesis. Conclusion: Measuring matrix metalloproteinase-9 in the AF appeared to be r eliable for diagnosing intra-amniotic infection. An elevated matrix metallo proteinase-9 concentration in the AF at a preterm gestational age may porte nd imminent delivery regardless of microbiologic confirmation of intra-amni otic infection. (C) 1999 by The American College of obstetricians and Gynec ologists.