- Objective: Among patients presenting with preterm labor and intact membranes, those with intra-amniotic inflammation have worse obstetrical and neonatal outcomes. The diagnosis of intra-amniotic inflammation can be easily made by detecting an elevated concentration of the cytokine interleukin (IL)-6 or the enzyme neutrophil collagenase, also known as matrix metalloproteinase (MMP)-8. The diagnostic performances of MMP-8 and IL-6 enzyme-linked immunosorbent assay (ELISA) tests are similar. Recently, a rapid test has become available for point-of-care determination of either MMP-8 or IL-6. The objectives of this study were to compare the diagnostic indices and predictive values between the rapid MMP-8 and IL-6 tests for the identification of intra-amniotic inflammation. Materials and methods: We performed a retrospective cohort study including 124 women with singleton pregnancies who presented with symptoms of preterm labor and underwent transabdominal amniocentesis for the evaluation of MIAC. MIAC was defined according to amniotic fluid culture results (aerobic and anaerobic bacteria as well as genital Mycoplasmas). Amniotic fluid white blood cell (WBC) counts were determined using a hemocytometer chamber. An elevated amniotic fluid MMP-8 concentration was assessed using Yoon's MMP-8 Check® (cutoff: 10ng/mL). An elevated amniotic fluid IL-6 concentration was scored when there was a positive result for the lateral flow-based immunoassay (cutoff of ≥745 pg/mL and ≥1,000 pg/mL). In order to objectively compare rapid MMP-8 and rapid IL-6 tests to identify intra-amniotic inflammation, an amniotic fluid WBC count of ≥50 cells/mm(3) was used to define intra-amniotic inflammation. Results: 1) The rapid tests had the same sensitivity for the detection of intra-amniotic inflammation [85.7% (18/21) for all]; 2) The specificity of the rapid MMP-8 test was higher than that of the rapid IL-6 test (using cut-off 745 pg/mL) for the identification of intra-amniotic inflammation [72.8% (75/103) vs. 64.1% (66/103); p < 0.05]; and 3) there were no differences in the sensitivity and specificity between the rapid MMP-8 test and the rapid IL-6 test (using the cut-off 1000 pg/mL) in the identification of intra-amniotic inflammation. Of 13 patients with discrepant results between the rapid MMP-8 and rapid IL-6 tests, two had a positive MMP-8 but a negative rapid IL-6 test, and both delivered preterm - one within 24 hours, and the other within 10 days - both had acute histologic chorioamnionitis. On the other hand, there were 11 patients with a positive rapid IL-6 but a negative rapid MMP-8 result of them 10 delivered preterm, 3 had acute histologic chorioamnionitis and 1 subacute chorionitis. Conclusion: We conclude that the rapid MMP-8 test has a better specificity than the rapid IL-6 (cut-off of 745 pg/mL) assay for the detection of intra-amniotic infection. Moreover, we observed that among patients who were not identified as having intra-amniotic infection or inflammation by the standard cultivation technique and amniotic fluid white blood cell count, those who had a positive MMP-8 rapid test delivered preterm and had acute histologic chorioamnionitis.