A low vaginal "pool" amniotic fluid glucose measurement is a predictive but not a sensitive marker for infection in women with preterm premature rupture of membranes

Amniotic fluid glucose level in PPROM pregnancies: a glance at the old friend

Introduction: To determine the amniotic fluid glucose levels in pregnancies complicated by preterm prelabor rupture of membranes (PPROM) based on the presence of microbial invasion of the amniotic cavity and/or intra-amniotic inflammation.Methods of Study: A total of 142 women with singleton pregnancies complicated by PPROM between gestational ages 24 + 0 and 36 + 6 weeks were included. Amniocentesis was performed at the time of admission. The assessments of microbial invasion of the amniotic cavity (using both cultivation and non-cultivation techniques) and intra-amniotic inflammation (amniotic fluid interleukin-6 levels ≥ 3000 pg/mL) were performed on all the women. Based on the presence of microbial invasion of the amniotic cavity and/or intra-amniotic inflammation, the women were further categorized into the subgroups: (i) intra-amniotic infection (the presence of both microbial invasion of the amniotic cavity and intra-amniotic inflammation); (ii) sterile intra-amniotic inflammation (the presence of intra-amniotic inflammation without microbial invasion of the amniotic cavity); (iii) colonization (the presence of microbial invasion of the amniotic cavity without intra-amniotic inflammation); and (iv) negative amniotic fluid (the absence of either microbial invasion of the amniotic cavity or intra-amniotic inflammation). Amniotic fluid glucose levels were assessed using enzymatic reference method with hexokinase.Results: There was a difference in the amniotic fluid glucose levels among the women with intra-amniotic infection, sterile intra-amniotic inflammation, colonization, and those with negative amniotic fluid (p < .0001). No difference was found in the amniotic fluid glucose levels between women with intra-amniotic infection and those with sterile intra-amniotic inflammation [infection: median 11.6 mg/dL (0.7 mmol/L) vs. sterile: median 6.3 mg/dL (0.4 mmol/L); p = .41] and between women with colonization and negative amniotic fluid [colonization: median 21.6 mg/dL (1.2 mmol/L) vs. negative: median 23.4 mg/dL (1.3 mmol/L; p = .67]. Women with intra-amniotic infection and sterile intra-amniotic inflammation had lower amniotic fluid glucose levels than women with colonization and with negative amniotic fluid in crude analysis as well as after adjustment for gestational age at sampling. Amniotic fluid glucose level of 10 mg/dL (0.56 mmol/L) was the optimal concentration for the identification of intra-amniotic inflammation in women with PPROM.Conclusions: The presence of intra-amniotic inflammation was associated with lower amniotic fluid glucose levels in singleton pregnancies complicated with PPROM. An amniotic fluid glucose level of 10 mg/dL (0.56 mmol/L) was the optimal concentration for the identification of intra-amniotic inflammation in PPROM pregnancies. In the absence of better amniotic fluid markers, amniotic glucose could be used as a marker of intra-amniotic inflammation, with very good specificity in PPROM pregnancies.

Measurement of Interleukin 8 in Cervicovaginal Fluid in Women With Preterm Premature Rupture of Membranes: A Comparison of Amniotic Fluid Samples

Cervicovaginal fluid (CVF) samples may be a feasible alternative to amniotic fluid (AF) sampling in women with preterm premature rupture of the membranes (PPROMs), because PPROM causes AF to spill into the CVF. We aimed to assess the correlation and limits of agreement of interleukin 8 (IL-8) levels between CVF and AF in women with PPROM and to compare the clinical value of CVF IL-8 to AF IL-8 for the prediction of microbial invasion of amniotic cavity (MIAC). A retrospective cohort observational study was conducted on 85 women with singleton pregnancies (24-34 weeks) presenting with PPROM. The CVF samples were obtained simultaneously with AF samples retrieved by transabdominal amniocentesis. The levels of IL-8 in paired CVF and AF samples were measured with enzyme-linked immunosorbent assay in the same plate in duplicate using the same dilutions. The prevalence of a positive AF culture was 40% (34 of 85). The CVF IL-8 levels were significantly and positively correlated with AF IL-8 levels ( r = 0.778). However, the level of agreement between CVF and AF IL-8 levels yielded a Cohen κ statistic of 0.276. Paired Student t test revealed that the difference between CVF and AF IL-8 levels was statistically significant. The area under the curve for AF IL-8 was significantly higher than that for CVF IL-8 ( P = .013). In women with PPROM, IL-8 levels in CVF were significantly correlated with, but were significantly different from, those in AF samples. The CVF IL-8 has moderate predictive capability for the risk of MIAC, but this is inferior to AF IL-8.

Vaginally obtained amniotic fluid samples in the diagnosis of subclinical chorioamnionitis

INTRODUCTION

Preterm birth is often caused by infection or inflammation. High concentration of lactate dehydrogenase and low concentration of glucose in amniotic fluid obtained by amniocentesis are associated with subclinical chorioamnionitis. We evaluated amniotic fluid lactate dehydrogenase and glucose concentrations in relation to histologic chorioamnionitis in vaginally obtained samples.

MATERIAL AND METHODS

In a prospective study, vaginally obtained amniotic fluid samples were collected from 53 women with preterm prelabor rupture of membranes at 23(+4) to 34(+5) weeks of gestation at University Hospital, Helsinki, Finland. Amniotic fluid lactate dehydrogenase and amniotic fluid glucose were measured by immunochemiluminometric assays. Histopathologic examination of placenta was performed. The main outcome measure was histologic chorioamnionitis.

RESULTS

Median concentration of vaginally obtained amniotic fluid lactate dehydrogenase was higher in women with histologic chorioamnionitis than in women without (1400 IU/L vs. 784.5 IU/L, p = 0.005). By receiver operating characteristics curve the optimal cut-off for amniotic fluid lactate dehydrogenase in relation to histologic chorioamnionitis was 1029 IU/L (sensitivity 65%, specificity 69%, positive predictive value 83% and negative predictive value 46%). Amniotic fluid lactate dehydrogenase concentrations showed striking fluctuation in repeat samples. Amniotic fluid glucose concentrations did not differ among women with or without histologic chorioamnionitis (0 mmol/L vs. 0.65 mmol/L, p = 0.20).

CONCLUSION

Elevated amniotic fluid lactate dehydrogenase was associated with histologic chorioamnionitis, but decreased amniotic fluid glucose was not. However, the clinical value of vaginally obtained amniotic fluid lactate dehydrogenase is limited because of high sample-to-sample variability. Better biomarkers for optimal timing of delivery in women with preterm prelabor rupture of membranes are needed.

Interpretation of amniotic fluid white blood cell count in "bloody tap" amniocenteses in women with symptoms of preterm labor

OBJECTIVE

To estimate whether blood-contaminated amniotic fluid affects the performance of white blood cell (WBC) count in diagnosing intraamniotic inflammation and infection.

METHODS

Three hundred fifty-seven consecutive women pregnant with singletons undergoing amniocentesis to rule out infection were enrolled prospectively. A "bloody tap" was defined as a red blood cell (RBC) count of 1,000 cells/mm or more. Proteomics analysis of amniotic fluid was used in this study as the standard for diagnosing inflammation. Infection was confirmed by positive amniotic fluid culture. An amniotic fluid WBC count correction formula was computed using maternal WBC count, hematocrit, and mean corpuscular volume.

RESULTS

The prevalence of a bloody tap amniocentesis was 22% (77 of 357). In the absence of inflammation, the amniotic fluid WBC count was significantly higher in bloody tap (median [interquartile range] 18 [9-58] cells/mm) compared with non-bloody tap specimens (4 [1-10] cells/mm; P<.001). The correction formula reversed this difference to a nonsignificant level (bloody tap 0 [0-17] compared with non-bloody tap 3 [1-10] cells/mm; P=.273). In the setting of inflammation, the observed WBC count of bloody tap samples (778 [197-2,062 cells/mm]) was significantly elevated compared with that of the non-bloody tap specimens (616 [105-1,730] cells/mm; P=.023). Correction of the WBC count in bloody tap amniocenteses improved the test accuracy and positive likelihood ratios for inflammation and infection. A correction algorithm was not useful in amniotic fluid specimens with less than 1,000/RBCs/mm or WBC counts more than 1,100 cells/mm. Given the nonlinear relationship between amniotic fluid WBC and RBC, for a rapid correction of WBC count, the number of neutrophils that need to be subtracted from the observed WBC count is variable.

CONCLUSION

In the setting of an amniotic fluid sample contaminated with 1,000 RBCs/mm or more, WBC count is a less accurate indicator of inflammation and infection. In such samples, correction of WBC count enhances diagnostic performance for inflammation and infection.

LEVEL OF EVIDENCE

II.

Diagnosis and management of clinical chorioamnionitis

Chorioamnionitis is a common complication of pregnancy associated with significant maternal, perinatal, and long-term adverse outcomes. Adverse maternal outcomes include postpartum infections and sepsis whereas adverse infant outcomes include stillbirth, premature birth, neonatal sepsis, chronic lung disease, and brain injury leading to cerebral palsy and other neurodevelopmental disabilities. Research in the past 2 decades has expanded understanding of the mechanistic links between intra-amniotic infection and preterm delivery as well as morbidities of preterm and term infants. Recent and ongoing clinical research into better methods for diagnosing, treating, and preventing chorioamnionitis is likely to have a substantial impact on short and long-term outcomes in the neonate.

Detection of feto-maternal infection/inflammation by the soluble receptor for advanced glycation end products (sRAGE): results of a pilot study

OBJECTIVE

The receptor for advanced glycation end products, RAGE, plays an important role in the pathogenesis of several diseases. sRAGE, soluble receptor for advanced glycation end products, is an inhibitor of the pathological effect mediated via RAGE. The aim of this study was to assess the usefulness of measuring sRAGE concentration in pregnant women with threatening preterm labor.

METHODS

Serum levels of sRAGE, interleukin-6 (IL-6) and routine markers of inflammation were determined in 46 pregnant women with threatening preterm labor, 35 healthy pregnant women and 15 non-pregnant controls.

RESULTS

Serum levels of sRAGE in healthy pregnant women were significantly lower than in non-pregnant controls (669+/-296 vs. 1929+/-727 pg/mL, P<0.05). Women with threatening preterm birth had a significantly higher concentration of serum sRAGE in comparison with healthy pregnant women (819+/-329 pg/mL vs. 669+/-296 pg/mL, P<0.05). Conversely, patients with PPROM had significantly lower levels of sRAGE compared with patients with threatening premature labor (600+/-324 pg/mL, P<0.05). sRAGE correlated negatively with leukocyte counts (r=-0.325, P<0.05).

CONCLUSIONS

sRAGE might be a new and promising marker of premature labor, especially with the symptoms of PPROM.

Value of placental microbial evaluation in diagnosing intra-amniotic infection

OBJECTIVE

To evaluate the ability of microbiologic and pathologic examination of the placenta to accurately diagnose intraamniotic infection and inflammation.

METHODS

One hundred eighty-three women with a clinically indicated amniocentesis were enrolled prospectively. We applied our analysis to 56 women with evidence of preterm labor or preterm premature rupture of membranes who delivered within 48 hours of amniotic fluid testing results. Twenty-three patients, assessed for fetal lung maturity in the third trimester, served as controls. Amniotic fluid was cultured for aerobic, anaerobic, Ureaplasma, and Mycoplasma species. We used mass spectrometry to assess the degree of intraamniotic inflammation (Mass Restricted scoring). After delivery, microbiologic and histologic studies of the placenta were performed. These results were interpreted in comparison with the direct microbiologic and inflammatory analysis of the amniotic fluid. A sample size of 45 patients was required to show a test accuracy of 80% or more.

RESULTS

Ninety-two percent of women with positive amniotic fluid cultures tested with at least one positive placenta culture. Eighty percent of women who had negative amniotic fluid cultures also tested with a positive placenta culture. The accuracy of placental cultures in predicting amniotic fluid infection varied from 44% to 57%. Placental pathology showed an accuracy of only 58% in diagnosing intraamniotic inflammation.

CONCLUSION

Placental microbiologic and histologic studies poorly reflect the infectious and inflammatory status of the amniotic fluid. Results of such studies should be interpreted with caution in the management and future counseling of women with preterm labor or preterm premature rupture of membranes.

LEVEL OF EVIDENCE

II.