Rapid evaluation of the absence of inflammation after rupture of membranes

Diagnostic value of Chorioquick for detecting chorioamnionitis in women with premature rupture of membranes

OBJECTIVE

To determine the accuracy of a semi-quantitative interleukin-6 (IL-6) vaginal secretion rapid test (Chorioquick) for detecting chorioamnionitis in women with premature rupture of membranes (PROM).

METHODS

A prospective cohort study in five tertiary hospitals in Nigeria involved women with confirmed PROM at term and preterm PROM with or without suspected chorioamnionitis from August 1, 2017, to October 31, 2018. Cervicovaginal fluid samples were tested for chorioamnionitis using the Chorioquick test. Samples were repeated at decision to deliver. The test was considered positive if at least the indicator 'IL-6 low' of the three Chorioquick biomarkers (low, medium, high) was positive, or negative if none of the biomarkers were positive. Chorioamnionitis was histologically confirmed post-delivery using three tissue samples. Primary outcome measures were sensitivity, specificity, and accuracy.

RESULTS

Of 73 women, on histological confirmation, 39 were true positive and 29 were true negative (for chorioamnionitis) to the Chorioquick test at repeat assessment. Overall, the Chorioquick test had a sensitivity of 97.5% (95% confidence interval [CI] 85.3-99.9), specificity 87.9% (70.9-96.0), and accuracy 93.2% (79.5-99.1). Sub-group analysis of women <37 weeks of pregnancy showed a sensitivity of 100.0% (95% CI 83.4-100.0), specificity of 91.3% (70.5-98.5), and accuracy of 95.8% (82.5-99.5). Triple positive samples were 100.0% specific in all gestations.

CONCLUSION

Chorioquick showed favorable utility for detecting chorioamnionitis in PROM and could be a reliable, non-invasive rapid tool in a real-world clinical setting.

Comparison of rapid MMP-8 and interleukin-6 point-of-care tests to identify intra-amniotic inflammation/infection and impending preterm delivery in patients with preterm labor and intact membranes. J Matern Fetal Neonatal Med 2018;31:228-244. [PMID: 28081646 PMCID: PMC5769687 DOI: 10.1080/14767058.2017.1281904]

OBJECTIVE

Among patients presenting with preterm labor and intact membranes, those with intra-amniotic inflammation have adverse obstetrical and neonatal outcomes. The diagnosis of intra-amniotic inflammation can easily be 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 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 in patients with preterm labor and intact membranes.

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 microbial invasion of the amniotic cavity (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: 10 ng/mL). An elevated amniotic fluid IL-6 concentration was scored when there was a positive result for the lateral flow-based immunoassay (cutoff: ≥745 pg/mL and ≥1000 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/mm3 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 (cutoff: 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 (cutoff: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 h, and the other within 10 days - and 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: 10 delivered preterm, 3 had acute histologic chorioamnionitis and 1 had subacute chorionitis.

CONCLUSION

We conclude that the rapid MMP-8 test has a better specificity than the rapid IL-6 (cutoff: 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 WBC count, those who had a positive MMP-8 rapid test delivered preterm and had acute histologic chorioamnionitis.

Vaginal fluid interleukin-6 concentrations as a point-of-care test is of value in women with preterm prelabor rupture of membranes

BACKGROUND

Preterm prelabor rupture of membranes is frequently complicated/accompanied by infection and inflammation in the amniotic cavity. A point-of-care determination of amniotic fluid interleukin-6 has been shown to be a potentially clinically useful approach to assess inflammatory status of the amniotic cavity. Amniocentesis in preterm prelabor rupture of membranes is not broadly used in clinical practice, and therefore, a shift toward a noninvasive amniotic fluid sampling method is needed.

OBJECTIVE

The first aim of this study was to evaluate the association between the point-of-care vaginal and amniotic fluid interleukin-6 concentrations in fresh unprocessed samples obtained simultaneously. The second goal was to determine the diagnostic indices and predictive value of the point-of-care assessment of vaginal fluid interleukin-6 concentration in the identification of microbial invasion of the amniotic cavity, intraamniotic inflammation, and microbial-associated intraamniotic inflammation in patients with preterm prelabor rupture of membranes.

STUDY DESIGN

A prospective cohort study was conducted in women with singleton gestation complicated by preterm prelabor rupture of membranes at between 24+0 and 36+6 weeks. A total of 153 women with singleton pregnancies were included in this study. Vaginal fluid was obtained from the posterior vaginal fornix by aspiration with a sterile urine sample tube with a suction tip. Amniotic fluid was obtained by transabdominal amniocentesis. Interleukin-6 concentrations were assessed with a lateral flow immunoassay in both fluids immediately after sampling. Microbial invasion of the amniotic cavity was determined based on a positive polymerase chain reaction analysis. Intraamniotic inflammation was defined as an amniotic fluid point-of-care interleukin-6 concentration ≥745 pg/mL.

RESULTS

Several results were obtained in this study. First, it was possible to perform the point-of-care assessment of interleukin-6 in vaginal fluid in 92% of the women (141 of 153), and only those women were included in the analyses. Second, the rate of microbial invasion of the amniotic cavity and intraamniotic inflammation was 26% (36 of 141) and 19% (27 of 141), respectively. Microbial-associated intraamniotic inflammation was identified in 12% of the women (17 of 141). Third, a strong positive correlation was found between the interleukin-6 concentrations in vaginal and amniotic fluids (Spearman rho 0.68; P < .0001). Fourth, the presence of microbial invasion of the amniotic cavity, intraamniotic inflammation, or microbial-associated intraamniotic inflammation was associated with higher vaginal fluid interleukin-6 concentrations in both crude and adjusted analyses. Fifth, a vaginal fluid interleukin-6 concentration of 2500 pg/mL was determined to be the best cutoff value for the identification of microbial invasion of the amniotic cavity (sensitivity of 53% [19 of 36], specificity of 89% [93 of 104], positive predictive value of 63% [19 of 30], negative predictive value of 85% [93 of 110], positive likelihood ratio of 5.0 [95% confidence interval, 2.5-9.5], and negative likelihood ratio of 0.5 [95% confidence interval, 0.4-0.8]); intraamniotic inflammation (sensitivity of 74% [20/27], specificity of 91% [104/114], positive predictive value of 67% [20 of 30], negative predictive value of 94% [104 of 111], positive likelihood ratio of 8.4 [95% confidence interval, 4.5-15.9], and negative likelihood ratio of 0.3 [95% confidence interval, 0.2-0.5]); and microbial-associated intraamniotic inflammation (sensitivity of 100% [17 of 17], specificity of 90% [111 of 124), positive predictive value of 57% [17 of 30], negative predictive value of 100% [111 of 111], positive likelihood ratio of 9.5 [95% confidence interval, 5.7-16.0], and negative likelihood ratio of 0).

CONCLUSION

The point-of-care assessment of interleukin-6 in vaginal fluid is an easy, rapid, noninvasive, and inexpensive method for the identification of intraamniotic inflammation and microbial-associated intraamniotic inflammation in preterm prelabor rupture of membranes pregnancies, showing good specificity and negative predictive value.

Cytokines in noninvasively obtained amniotic fluid as predictors of fetal inflammatory response syndrome

BACKGROUND

In patients with preterm premature rupture of membranes, intrauterine inflammation and/or infection is frequently present, can lead to fetal inflammatory response syndrome, and is associated with adverse neonatal outcome. Clinical decision making requires balancing the potential benefits of pregnancy prolongation against the risk of intrauterine infection. Diagnostic tests in maternal serum are of moderate prediction value and amniocentesis is an invasive procedure. Therefore, markers obtained noninvasively would be helpful in patients with expectant management.

OBJECTIVES

To determine the predictive values of amniotic fluid interleukin-6 and tumor necrosis factor-α in vaginal secretions for fetal inflammatory response syndrome and/or histologic funisitis and for adverse neonatal outcome in patients with preterm premature rupture of membranes.

STUDY DESIGN

In this prospective multicenter case-control study, vaginal secretions were sampled daily with a noninvasive method from 99 women with preterm premature rupture of membranes and expectant management. Amniotic fluid interleukin-6 and tumor necrosis factor-α were measured by 2 different immunoassays (an automated chemiluminescent enzyme immunoassay and a lateral flow immunoassay). After delivery, patients were divided into a control or a fetal inflammatory response syndrome group according to neonatal interleukin-6 in cord plasma and/or the presence of funisitis. Univariate and multivariate regression analyses were performed and prediction models were developed by calculating receiver operating characteristic curves.

RESULTS

Gestational age at delivery was lower and latency period was longer in the fetal inflammatory response syndrome group compared to the control group. The strongest risk factor for composite adverse neonatal outcome was fetal inflammatory response syndrome (odds ratio, 2.48; confidence interval, 1.40-4.38). The median concentrations of amniotic fluid interleukin-6 and tumor necrosis factor-α in vaginal secretions were significantly higher in the fetal inflammatory response group compared to the control group in both immunoassays (P < .001). The area under the curve of the clinical reference model (including common clinical parameters) was 0.66. Adding interleukin-6 and tumor necrosis factor-α into the model improved the area under the curve to 0.92 (in both assays, interleukin-6 IMMULITE and QuickLine); 0.87 (tumor necrosis factor-α IMMULITE) and 0.94 (tumor necrosis factor-α QuickLine), respectively.

CONCLUSION

The strongest risk factor for worse neonatal outcome (composite neonatal outcome) was fetal inflammatory response syndrome. Amniotic fluid interleukin-6 and tumor necrosis factor-α seem to be good predictors for fetal inflammatory response syndrome and for histologic funisitis and may improve the clinical management of patients with preterm premature rupture of membranes. The noninvasive technique of sampling amniotic fluid from vaginal secretions facilitates daily measurements and bedside assessment of cytokines and is in this respect preferable to invasive amniocentesis.

Clinical chorioamnionitis at term IV: the maternal plasma cytokine profile

INTRODUCTION

Fever is a major criterion for clinical chorioamnionitis; yet, many patients with intrapartum fever do not have demonstrable intra-amniotic infection. Some cytokines, such as interleukin (IL)-1, IL-6, interferon-gamma (IFN-γ), and tumor necrosis factor alpha (TNF-α), can induce a fever. The objective of this study was to determine whether maternal plasma concentrations of cytokines could be of value in the identification of patients with the diagnosis of clinical chorioamnionitis at term who have microbial-associated intra-amniotic inflammation.

METHODS

A retrospective cross-sectional study was conducted, including patients with clinical chorioamnionitis at term (n=41; cases) and women in spontaneous labor at term without clinical chorioamnionitis (n=77; controls). Women with clinical chorioamnionitis were classified into three groups according to the results of amniotic fluid culture, broad-range polymerase chain reaction coupled with electrospray ionization mass spectrometry (PCR/ESI-MS), and amniotic fluid IL-6 concentration: 1) no intra-amniotic inflammation; 2) intra-amniotic inflammation without detectable microorganisms; or 3) microbial-associated intra-amniotic inflammation. The maternal plasma concentrations of 29 cytokines were determined with sensitive and specific V-PLEX immunoassays. Nonparametric statistical methods were used for analysis, adjusting for a false discovery rate of 5%.

RESULTS

1) The maternal plasma concentrations of pyrogenic cytokines (IL-1β, IL-2, IL-6, IFN-γ, and TNF-α) were significantly higher in patients with clinical chorioamnionitis at term than in those with spontaneous term labor without clinical chorioamnionitis; 2) the maternal plasma concentrations of cytokines were not significantly different among the three subgroups of patients with clinical chorioamnionitis (intra-amniotic inflammation with and without detectable bacteria and those without intra-amniotic inflammation); and 3) among women with the diagnosis of clinical chorioamnionitis, but without evidence of intra-amniotic inflammation, the maternal plasma concentrations of pyrogenic cytokines were significantly higher than in patients with spontaneous labor at term. These observations suggest that a fever can be mediated by increased circulating concentrations of these cytokines, despite the absence of a local intra-amniotic inflammatory response.

CONCLUSIONS

1) The maternal plasma concentrations of pyrogenic cytokines (e.g. IL-1β, IL-2, IL-6, IFN-γ, and TNF-α) are higher in patients with intra-partum fever and the diagnosis of clinical chorioamnionitis at term than in those in spontaneous labor at term without a fever; and 2) maternal plasma cytokine concentrations have limited value in the identification of patients with bacteria in the amniotic cavity. Accurate assessment of the presence of intra-amniotic infection requires amniotic fluid analysis.

A rapid interleukin-6 bedside test for the identification of intra-amniotic inflammation in preterm labor with intact membranes

Objective: Preterm birth is associated with 5–18% of pregnancies and is the leading cause of neonatal morbidity and mortality. Amniotic fluid (AF) interleukin-6 (IL-6) is a key cytokine for the identification of intra-amniotic inflammation, and patients with an elevated AF IL-6 are at risk for impending preterm delivery. However, results of the conventional method of measurement (enzyme-linked immunosorbent assay; ELISA) are usually not available in time to inform care. The objective of this study was to determine whether a point of care (POC) test or lateral-flow-based immunoassay for measurement of AF IL-6 concentrations can identify patients with intra-amniotic inflammation and/or infection and those destined to deliver spontaneously before term among women with preterm labor and intact membranes.

Methods: One-hundred thirty-six women with singleton pregnancies who presented with symptoms of preterm labor and underwent amniocentesis were included in this study. Amniocentesis was performed at the time of diagnosis of preterm labor. AF Gram stain and AF white blood cell counts were determined. Microbial invasion of the amniotic cavity (MIAC) was defined according to the results of AF culture (aerobic and anaerobic as well as genital mycoplasmas). AF IL-6 concentrations were determined by both lateral flow-based immunoassay and ELISA. The primary outcome was intra-amniotic inflammation, defined as AF ELISA IL-6 ≥ 2600 pg/ml.

Results: (1) AF IL-6 concentrations determined by a POC test have high sensitivity (93%), specificity (91%) and a positive likelihood ratio of 10 for the identification of intra-amniotic inflammation by using a threshold of 745 pg/ml; (2) the POC test and ELISA for IL-6 perform similarly in the identification of MIAC, acute inflammatory lesions of placenta and patients at risk of impending spontaneous preterm delivery.

Conclusion: A POC AF IL-6 test can identify intra-amniotic inflammation in women who present with preterm labor and intact membranes and those who will subsequently deliver spontaneously before 34 weeks of gestation. Results can be available within 20 min – this has important clinical implications and opens avenues for early diagnosis as well as treatment of intra-amniotic inflammation/infection.

A point of care test for the determination of amniotic fluid interleukin-6 and the chemokine CXCL-10/IP-10

OBJECTIVE

Intra-amniotic inflammation is a mechanism of disease implicated in preterm labor, preterm prelabor rupture of membrane, cervical insufficiency, a short cervix, and idiopathic vaginal bleeding. Determination of interleukin (IL)-6 with immunoassays has been proven for more than two decades to be an excellent method for the detection of intra-amniotic inflammation. However, assessment of IL-6 for this indication has been based on immunoassays which are not clinically available, and this has been an obstacle for the implementation of this test in clinical practice. It is now possible to obtain results within 20 min with a point of care (POC) test which requires minimal laboratory support. This test is based on lateral flow-based immunoassay. The objective of this study was to compare amniotic fluid (AF) IL-6 and interferon-γ - inducible protein 10 (IP-10 or CXCL-10) concentrations determined using lateral flow-based immunoassay or POC test and standard enzyme-linked immunosorbent assay (ELISA) techniques.

MATERIAL AND METHODS

AF samples were collected from patients with singleton gestations and symptoms of preterm labor (n = 20). AF IL-6 and IP-10 concentrations were determined by lateral flow-based immunoassay and ELISA. Intra-amniotic inflammation was defined as AF IL-6 ≥ 2.6 ng/ml. AF IL-6 and IP-10 concentrations between two assays were compared.

RESULTS

(1) Lateral flow-based immunoassay POC AF IL-6 and IP-10 test results were strongly correlated with concentrations of this cytokine/chemokine determined by ELISA (Spearman's ρ = 0.92 and 0.83, respectively, both p < 0.0001); (2) AF IL-6 concentrations determined by the lateral flow-based immunoassay test were, on average, 30% lower than those determined by ELISA, and the median difference was statistically significant (p < 0.0001); and (3) in contrast, AF IP-10 concentrations determined by the lateral flow-based immunoassay test were, on average, only 7% lower than those determined by ELISA, and the median difference was not statistically significant (p = 0.81).

CONCLUSION

AF IL-6 and IP-10 concentrations determined using a lateral flow-based immunoassay POC are strongly correlated with concentrations determined by conventional ELISA. This justifies further studies about the diagnostic indices and predictive values of this POC test.

Detection of microbial invasion of the amniotic cavity by analysis of cervicovaginal proteins in women with preterm labor and intact membranes

OBJECTIVE

Microbial invasion of the amniotic cavity (MIAC) is common in early preterm labor and is associated with maternal and neonatal infectious morbidity. MIAC is usually occult and is reliably detected only with amniocentesis. We sought to develop a noninvasive test to predict MIAC based on protein biomarkers in cervicovaginal fluid (CVF) in a cohort of women with preterm labor (phase 1) and to validate the test in an independent cohort (phase 2).

STUDY DESIGN

This was a prospective study of women with preterm labor who had amniocentesis to screen for MIAC. MIAC was defined by positive culture and/or 16S ribosomal DNA results. Nine candidate CVF proteins were analyzed by enzyme-linked immunosorbent assay. Logistic regression was used to identify combinations of up to 3 proteins that could accurately classify the phase 1 cohort (N = 108) into those with or without MIAC. The best models, selected by area under the curve (AUC) of the receiver operating characteristic curve in phase 1, included various combinations of interleukin (IL)-6, chemokine (C-X-C motif) ligand 1 (CXCL1), alpha fetoprotein, and insulin-like growth factor binding protein-1. Model performance was then tested in the phase 2 cohort (N = 306).

RESULTS

MIAC was present in 15% of cases in phase 1 and 9% in phase 2. A 3-marker CVF model using IL-6 plus CXCL1 plus insulin-like growth factor binding protein-1 had AUC 0.87 in phase 1 and 0.78 in phase 2. Two-marker models using IL-6 plus CXCL1 or alpha fetoprotein plus CXCL1 performed similarly in phase 2 (AUC 0.78 and 0.75, respectively), but were not superior to CVF IL-6 alone (AUC 0.80). A cutoff value of CVF IL-6 ≥463 pg/mL (which had 81% sensitivity in phase 1) predicted MIAC in phase 2 with sensitivity 79%, specificity 78%, positive predictive value 38%, and negative predictive value 97%.

CONCLUSION

High levels of IL-6 in CVF are strongly associated with MIAC. If developed into a bedside test or rapid laboratory assay, cervicovaginal IL-6 might be useful in selecting patients in whom the probability of MIAC is high enough to warrant amniocentesis or transfer to a higher level of care. Such a test might also guide selection of potential subjects for treatment trials.

A point of care test for interleukin-6 in amniotic fluid in preterm prelabor rupture of membranes: a step toward the early treatment of acute intra-amniotic inflammation/infection

OBJECTIVE

Preterm prelabor rupture of membranes (preterm PROM) accounts for 30-40% of spontaneous preterm deliveries and thus is a major contributor to perinatal morbidity and mortality. An amniotic fluid (AF) interleukin-6 (IL-6) concentration is a key cytokine for the identification of intra-amniotic inflammation, patients at risk of impending preterm delivery and adverse pregnancy complications. The conventional method to determine IL-6 concentrations in AF is an enzyme-linked immunosorbent assay (ELISA). However, this technique is not available in clinical settings, and the results may take several days. A lateral flow-based immunoassay, or point of care (POC) test, has been developed to address this issue. The objective of this study was to compare the performance of AF IL-6 determined by the POC test to that determined by ELISA for the identification of intra-amniotic inflammation in patients with preterm PROM.

MATERIALS AND METHODS

This retrospective cohort study includes 56 women with singleton pregnancies who presented with preterm PROM. Amniocentesis was performed at the time of diagnosis, and AF was analyzed using cultivation techniques for aerobic and anaerobic bacteria as well as genital mycoplasmas. AF Gram stain and AF white blood cell counts were determined. AF IL-6 concentrations were measured using both lateral flow-based immunoassay and ELISA. The primary outcome was intra-amniotic inflammation defined as AF ELISA IL-6 ≥ 2600 pg/ml. A previously determined cut-off of 745 pg/ml was used to define a positive POC test.

RESULTS

(1) The POC test for AF IL-6 concentrations had 97% sensitivity and 96% specificity for the identification of intra-amniotic inflammation, as defined using ELISA among patients with preterm PROM and (2) the diagnostic performance of the POC test for IL-6 was strongly correlated to that of an ELISA test for the identification of intra-amniotic inflammation and was equivalent for the identification of acute inflammatory placental lesions and microbial invasion of the amniotic cavity (MIAC).

CONCLUSION

A POC AF IL-6 test can identify intra-amniotic inflammation in patients with preterm PROM. Results can be available within 20 min - this makes it possible to implement interventions designed to treat intra-amniotic inflammation and improve pregnancy outcomes.

Bedside assessment of amniotic fluid interleukin-6 in preterm prelabor rupture of membranes

OBJECTIVE

The objective of the study was to determine the diagnostic indices and predictive values by bedside assessment of amniotic fluid interleukin-6 (IL-6) concentration in the identification of microbial invasion of the amniotic cavity (MIAC) and/or histological chorioamnionitis (HCA) in patients with preterm prelabor rupture of membranes.

STUDY DESIGN

One hundred twenty-four women with singleton pregnancies were included in this study. The amniotic fluid was sampled by transabdominal amniocentesis at the time of admission. IL-6 concentrations were assessed with an immunoassay.

RESULTS

The presence of MIAC, HCA, or the coexistence of both was associated with higher amniotic fluid concentrations of IL-6 in both a crude and adjusted analysis. The amniotic fluid concentration of IL-6 of 1000 pg/mL was determined to be the best cutoff value for the prediction of MIAC (sensitivity of 50%, specificity of 95%, positive predictive value of 82%, negative predictive value of 81%, and likelihood ratio of 8.4) or both MIAC and HCA (sensitivity of 60%, specificity of 94%, positive predictive value of 75%, negative predictive value of 88%, and likelihood ratio of 9.4).

CONCLUSION

The bedside assessment of amniotic fluid IL-6 seems to be an easy, rapid, and inexpensive method for the prediction of MIAC or both MIAC and HCA in pregnancies complicated by preterm prelabor rupture of membranes.