Fetal fibronectin detection as a predictor of preterm birth in actual clinical practice

AACC Guidance Document on Laboratory Testing for the Assessment of Preterm Delivery

Identifying women with preterm labor who will go on to deliver prematurely is crucial to improving outcomes for mother and baby and for saving healthcare resources. Even among those with symptoms, the number of women who deliver preterm is low, and thus the low positive predictive value (PPV) and high negative predictive value (NPV) associated with available biomarkers does not substantially reduce the uncertainty of the clinical diagnosis. While there is some promise in the use of fetal fibronectin (fFN), interleukin 6 (IL-6), or placental alpha microglobulin 1 (PAMG-1) for predicting preterm birth (PTB), their use is unlikely to provide considerable clinical value in populations with a low prevalence. To provide real clinical benefit, a biomarker must demonstrate a high PPV to allow identification of the minority of symptomatic women who will deliver prematurely. As none of the currently available biomarkers exhibit this performance characteristic, we do not recommend their routine clinical use in populations with a pre-test probability of PTB of <5%. Limiting biomarker testing to only high-risk women identified on the basis of cervical length or other characteristics will increase the pre-testprobability in the tested population, thereby improving PPV. PAMG-1 is associated with a higher PPV than fFN and may show clinical utility in populations with a higher pre-test probability, but further work is required to conclusively demonstrate improved outcomes in this patient group.

A high concentration of fetal fibronectin in cervical secretions increases the risk of intra-amniotic infection and inflammation in patients with preterm labor and intact membranes

Objective To determine whether the risk of intra-amniotic infection/inflammation and spontaneous preterm delivery (SPTD) varies as a function of the concentration of cervical fetal fibronectin (fFN) in patients with preterm labor and intact membranes. Methods This prospective study included 180 patients with preterm labor and intact membranes who had a sample collected for quantitative fFN measurement and underwent amniocentesis. Amniotic fluid was cultured for aerobic and anaerobic bacteria and genital mycoplasmas. Intra-amniotic inflammation was defined as an amniotic fluid matrix metalloproteinase-8 concentration >23 ng/mL. Results (1) The prevalence of intra-amniotic infection/inflammation and SPTD within 7 days was 32.2% (58/180) and 33.9% (61/178), respectively; (2) The higher the fFN concentration, the greater the risk of intra-amniotic infection/inflammation and SPTD within 7 days (P<0.001, respectively); (3) An fFN concentration 150 ng/mL had a better diagnostic performance than an fFN 50 ng/mL in the identification of intra-amniotic infection/inflammation and SPTD within 7 days; (4) Among the patients with an fFN <50 ng/mL, intra-amniotic infection/inflammation was identified in 7.6% (6/79) of patients and 66.7% (4/6) delivered within 7 days. Conclusion The higher the concentration of fFN, the greater the risk of intra-amniotic infection/inflammation and SPTD in patients with preterm labor and intact membranes.

Prediction of preterm delivery in symptomatic women using PAMG-1, fetal fibronectin and phIGFBP-1 tests: systematic review and meta-analysis

OBJECTIVE

To assess the accuracy of placental alpha microglobulin-1 (PAMG-1), fetal fibronectin (fFN) and phosphorylated insulin-like growth factor-binding protein-1 (phIGFBP-1) tests in predicting spontaneous preterm birth (sPTB) within 7 days of testing in women with symptoms of preterm labor, through a systematic review and meta-analysis of the literature. The test performance of each biomarker was also assessed according to pretest probability of sPTB ≤ 7 days.

METHODS

The Cochrane, MEDLINE, PubMed and ResearchGate bibliographic databases were searched from inception until October 2017. Cohort studies that reported on the predictive accuracy of PAMG-1, fFN and phIGFBP-1 for the prediction of sPTB within 7 days of testing in women with symptoms of preterm labor were included. Summary receiver-operating characteristics (ROC) curves and sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and positive (LR+) and negative (LR-) likelihood ratios were generated using indirect methods for the calculation of pooled effect sizes with a bivariate linear mixed model for the logit of sensitivity and specificity, with each diagnostic test as a covariate, as described by the Cochrane Handbook for Systematic Reviews of Diagnostic Test Accuracy.

RESULTS

Bivariate mixed model pooled sensitivity of PAMG-1, fFN and phIGFBP-1 for the prediction of sPTB ≤ 7 days was 76% (95% CI, 57-89%), 58% (95% CI, 47-68%) and 93% (95% CI, 88-96%), respectively; pooled specificity was 97% (95% CI, 95-98%), 84% (95% CI, 81-87%) and 76% (95% CI, 70-80%) respectively; pooled PPV was 76.3% (95% CI, 69-84%) (P < 0.05), 34.1% (95% CI, 29-39%) and 35.2% (95% CI, 31-40%), respectively; pooled NPV was 96.6% (95% CI, 94-99%), 93.3% (95% CI, 92-95%) and 98.7% (95% CI, 98-99%), respectively; pooled LR+ was 22.51 (95% CI, 15.09-33.60) (P < 0.05), 3.63 (95% CI, 2.93-4.50) and 3.80 (95% CI, 3.11-4.66), respectively; and pooled LR- was 0.24 (95% CI, 0.12-0.48) (P < 0.05), 0.50 (95% CI, 0.39-0.64) and 0.09 (95% CI, 0.05-0.16), respectively. The areas under the ROC curves for PAMG-1, fFN and phIGFBP-1 for sPTB ≤ 7 days were 0.961, 0.874 and 0.801, respectively.

CONCLUSIONS

In the prediction of sPTB within 7 days of testing in women with signs and symptoms of preterm labor, the PPV of PAMG-1 was significantly higher than that of phIGFBP-1 or fFN. Other diagnostic accuracy measures did not differ between the three biomarker tests. As prevalence affects the predictive performance of a diagnostic test, use of a highly specific assay for a lower-prevalence syndrome such as sPTB may optimize management. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

The fetal fibronectin test: 25 years after its development, what is the evidence regarding its clinical utility? A systematic review and meta-analysis

Background: The identification of women at risk for preterm birth should allow interventions which could improve neonatal outcome. Fetal fibronectin, a glycoprotein which acts normally as glue between decidua and amniotic membranes could be a good marker of impending labour when its concentration in cervicovaginal secretions between 22 and 36 weeks of gestation is ≥50 ng/mL. Many authors worldwide have tested this marker with many different methodologies and clinical settings, but conclusions about its clinical use are mixed. It is time for a comprehensive update through a systematic review and meta-analysis.Methods: We searched PubMed, Cochrane Library, and Embase, supplemented by manual search of bibliographies of known primary and review articles, international conference papers, and contact with experts from 1-1990 to 2-2018. We have selected all type of studies involving fetal fibronectin test accuracy for preterm delivery. Two authors independently extracted data about study characteristics and quality from identified publications. Contingency tables were constructed. Reference standards were preterm delivery before 37, 36, 35, 34, and 32 weeks, within 28, 21, 14, or 7 d and within 48 h. Data were pooled to produce summary likelihood ratios for positive and negative tests results.Results: One hundred and ninety-three primary studies were identified allowing analysis of 53 subgroups. In all settings, none of the summary likelihood ratios were >10 or <0.1, thus indicating moderate prediction, particularly in asymptomatic women and in multiple gestations.Conclusions: The fetal fibronectin test should not be used as a screening test for asymptomatic women. For high-risk asymptomatic women, and especially for women with multiple pregnancies, the performance of the fetal fibronectin test was also too low to be clinically relevant. Consensual use as a diagnostic tool for women with suspected preterm labor, the best use policy probably still depends on local contingencies, future cost-effectiveness analysis, and comparison with other more recent available biochemical markers.

Bio-functionalized magnetic nanoparticles for the immunoassay of fetal fibronectin: a feasibility study for the prediction of preterm birth

Preterm birth is an important cause of perinatal morbidity and mortality. Various biomarkers in cervicovaginal secretions related to preterm birth have been investigated, of which foetal fibronectin (fFN) shows the greatest potential because of its high negative predictive value. The immunomagnetic reduction (IMR) assay has emerged as a novel quantitative method to detect biomarkers. In this prospective case-control study, we analysed 33 samples of cervicovaginal secretions from pregnant women between 22 and 34 weeks of gestation at high risk of preterm birth. Seventeen samples were from women with term deliveries and 16 from those with preterm deliveries. The fFN concentration in each sample was measured using both an IMR assay and enzyme-linked immunosorbent assay (ELISA). The low detection limits of the IMR assay and ELISA were 0.0001 ng/mL and 0.789 ng/mL, respectively. The sensitivity and specificity of the IMR assay were 0.833 and 0.944, respectively, compared to 0.583 and 0.611 by ELISA. Our results suggest that measuring the concentration of fFN with the IMR assay is a good alternative method to accurately predict the risk of preterm birth.

The short-term prediction of preterm birth: a systematic review and diagnostic metaanalysis

OBJECTIVE

To assess the diagnostic accuracy of fetal fibronectin (fFN), fetal breathing movements (FBM), and cervical length (CL) for the short-term prediction of preterm birth in symptomatic patients.

STUDY DESIGN

Diagnostic metaanalysis using bivariate methods.

RESULTS

Pooled sensitivities for fFN, FBM, and CL for delivery within 48 hours of testing were 0.62 (95% confidence interval [CI], 0.43-0.78), 0.75 (95% CI, 0.57-0.87) and 0.77 (95% CI, 0.54-0.90), respectively. Pooled specificities for fFN, FBM, and CL for delivery within 48 hours were 0.81 (95% CI, 0.74-0.86), 0.93 (95% CI, 0.75-0.98) and 0.88 (95% CI, 0.84-0.91). Pooled sensitivities for fFN, FBM, and CL for delivery within 7 days were 0.75 (95% CI, 0.69-0.80), 0.67 (95% CI, 0.43-0.84), and 0.74 (95% CI, 0.58-0.85). Pooled specificities for fFN, FBM, and CL for delivery within 7 days were 0.79 (95% CI, 0.76-0.83), 0.98 (95% CI, 0.83-1.00) and 0.89 (95% CI, 0.85-0.92). Based on a pretest probability of 10% for delivery within 48 hours, posttest probabilities (positive and negative) were 27% and 5% for fFN, 54% and 3% for fFN, and 42% and 3% for CL. For a pretest probability of 20% for delivery within 7 days, posttest probabilities (positive and negative) were 48% and 7% for fFN, 89% and 8% for FBM, and 63% and 7% for CL.

CONCLUSION

In symptomatic patients, for fFN, absence of FBM, and CL have diagnostic use as predictors of delivery within 48 hours and within 7 days of testing. Absence of FBM appears to be the best test for predicting preterm birth.

IMMUNOMAGNETIC REDUCTION FOR FETAL FIBRONECTIN DETECTION — A NOVEL METHOD TO DETECT THE PRETERM BIOMARKER

Preterm birth is the main cause of perinatal morbidity and mortality throughout the world. Fetal fibronectin (fFN) is one type of glycoprotein detected in the interface of the choriodecidual junction. Preterm labor is related to the disruption of the choriodecidual junction and thus fFN releases in the ectocervix or posterior vaginal fornix. Quantization of fFN can assist the diagnosis and prevention of preterm birth.

In this work, we developed an immunoassay, the immunomagnetic reduction (IMR), to quantitatively detect fFN. It was found that the low detection limit for fFN via IMR is less than 10 ng/ml, which is much lower than clinic criteria 50 ng/ml. In addition to the high sensitivity, IMR assay shows such merits as low cost and high reliability for detecting fFN.

Clinical application of surface plasmon resonance-based biosensors for fetal fibronectin detection

Preterm birth is the leading cause of perinatal morbidity and mortality. Fetal fibronectin (fFN), a glycoprotein in the extracellular matrix of the amniotic membranes, is the most powerful biomarker for predicting the risk of preterm birth. Biosensors using the surface plasmon resonance (SPR) response are potentially useful in quantitatively measuring molecules. We established a standard calibration curve of SPR intensity against fFN concentration and used the SPR-based biosensor to detect fFN concentrations in the cervicovaginal secretions of pregnant women between 22 and 34 weeks of gestation. The calibration curve extends from 0.5 ng/mL to 100 ng/mL with an excellent correlation (R(2) = 0.985) based on standard fFN samples. A cutoff value of 50 ng/mL fFN concentration in commercial ELISA kits corresponds to a relative intensity of 17 arbitrary units (a.u.) in SPR. Thirty-two pregnant women were analyzed in our study. In 11 women, the SPR relative intensity was greater than or equal to 17 a.u., and in 21 women, the SPR relative intensity was less than 17 a.u. There were significant differences between the two groups in regular uterine contractions (p = 0.040), hospitalization for tocolysis (p = 0.049), and delivery weeks (p = 0.043). Our prospective study concluded that SPR-based biosensors can quantitatively measure fFN concentrations. These results reveal the potential utility of SPR-based biosensors in predicting the risk of preterm birth.

Plasma fibronectin concentration in obese/overweight pregnant women: a possible risk factor for preeclampsia

Plasma fibronectin (FN) levels in obese/overweight and non-obese pregnant women were evaluated as a possible risk factor for preeclampsia. A total of one hundred and sixty three pregnant women attending antenatal clinic at University of Calabar Teaching Hospital participated in the study and sixty non-pregnant women served as control. About 77 (47.24%) of the pregnant women were followed up for any subsequent development of preeclampsia during the pregnancy. Fibronectin levels in plasma were measured by ELISA assay and serum total protein, urea and creatinine were determined spectrophotometrically. The mean plasma FN concentration of non-obese pregnant women in first trimester was lower than those of the non-pregnant women by 24%, but however, increased to the non-pregnant level in second and third trimesters. Obese/overweight pregnant women had significantly (P < 0.05) higher values than non-obese pregnant women in second and third trimesters. FN in obese/overweight pregnant women correlated positively with mean arterial blood pressure (MAP: r = 0.414, P = 0.04). About 28.57% of the pregnant women with FN above cut off point of 330 μg/ml at 18-24 weeks of gestation developed preeclampsia. This value increased to 40.0% when only the obese/overweight women were considered. On analysis of both fibronectin >330 μg/ml and MAP > 90, the predictive value increased to 66.7%. We therefore conclude that elevated FN may be regarded as a risk factor of preeclampsia especially among the obese women.

Fetal fibronectin as a predictor of spontaneous preterm birth: a European perspective

Preterm birth (PTB) is estimated to account for 6-10% of all births worldwide with 13 million PTBs occurring annually and 1 million resulting in death. The diagnosis of spontaneous preterm labor and accurate prediction of preterm delivery is notoriously difficult. Identification of effective risk assessment markers can potentially improve outcomes by enabling targeted therapy while allowing efficient use of resources and avoiding unnecessary interventions. Advances in perinatal medicine have not reduced PTB and effective measures that improve outcome are yet to be established. However, considerable progress has been made in the development of accurate methods (fetal fibronectin and cervical length assessment) to predict PTB in both symptomatic and asymptomatic high-risk women. The excellent negative predictive value of fFN has the ability to facilitate decision-making regarding admission, in utero transfer, administration of antenatal corticosteroids and/or tocolysis and has been shown to be cost-effective. This review describes the European perspective on the use of fFN and describes ongoing European clinical studies, which are appropriately designed with meaningful endpoints, which will undoubtedly facilitate a better understanding of test accuracy and cost-effectiveness within different populations.

Biochemical markers for the prediction of preterm delivery

Preterm delivery is the largest contributor to perinatal morbidity and mortality throughout the world. In the United States, nearly 1 in every 8 infants is born prematurely. Although a portion of these births are indicated preterm deliveries, the frequency of spontaneous preterm birth has remained largely constant over the past 50 years.

Recurrent preterm birth

Recurrent preterm birth is frequently defined as two or more deliveries before 37 completed weeks of gestation. The recurrence rate varies as a function of the antecedent for preterm birth: spontaneous versus indicated. Spontaneous preterm birth is the result of either preterm labor with intact membranes or preterm prelabor rupture of the membranes. This article reviews the body of literature describing the risk of recurrence of spontaneous and indicated preterm birth. Also discussed are the factors which modify the risk for recurrent spontaneous preterm birth (a short sonographic cervical length and a positive cervicovaginal fetal fibronectin test). Patients with a history of an indicated preterm birth are at risk not only for recurrence of this subtype, but also for spontaneous preterm birth. Individuals of black origin have a higher rate of recurrent preterm birth.

Biochemical markers for the prediction of preterm labor

Premature labor and subsequent premature delivery is the major cause of perinatal death in the world. Numerous risk factors identify patients at jeopardy for preterm labor, but with poor sensitivity. Several biologic and biochemical markers have been recently studied that may allow early identification of patients at risk of preterm delivery. Although two markers have received Food and Drug Administration approval, a number of other tests also may ultimately prove useful.

Cervicovaginal fibronectin improves the prediction of preterm delivery based on sonographic cervical length in patients with preterm uterine contractions and intact membranes

OBJECTIVE

The purpose of this study was to examine the diagnostic performance of ultrasonographic measurement of the cervical length and vaginal fetal fibronectin determination in the prediction of preterm delivery in patients with preterm uterine contractions and intact membranes.

STUDY DESIGN

Ultrasound examination of the cervical length and fetal fibronectin determination in vaginal secretions were performed in 215 patients admitted with preterm uterine contractions (22-35 weeks) and cervical dilatation of </=3 cm. Outcome variables were the occurrence of preterm delivery within 48 hours, 7 days, and 14 days of admission, delivery </=32 and </=35 weeks, as well as the admission-to-delivery interval. Statistical analysis included chi-square test, receiver-operator characteristic (ROC) curve analysis, logistic regression, and survival analysis.

RESULTS

The overall prevalence of preterm delivery </=35 weeks was 20% (43/215). The prevalence of spontaneous preterm delivery within 48 hours, 7 days, and 14 days of admission, and delivery </=32 and </=35 weeks were 7.9% (17/215), 13.0% (28/215), 15.8% (34/215), 8.9% (9/101), and 15.8% (34/215), respectively. ROC curve analysis and contingency tables showed a significant relationship between the occurrence of preterm delivery and both cervical length and fetal fibronectin results ( P < .01 for each). Both tests performed comparably in the prediction of spontaneous preterm delivery. However, when fetal fibronectin results were added to those of cervical length (<30 mm), a significant improvement in the prediction of preterm delivery was achieved.

CONCLUSION

Fetal fibronectin adds prognostic information to that provided by sonographic measurement of the cervical length in patients with preterm uterine contractions and intact membranes.

Biochemical predictors of preterm labor: fetal fibronectin and salivary estriol

Preterm birth is a major complication of pregnancy and remains a leading cause of neonatal morbidity and mortality worldwide. Improvements in the authors' understanding of the pathophysiology of preterm labor have led to the development of novel diagnostic tools of use to identify women at greatest risk for preterm birth. Currently two FDA-approved biochemical tests are available in the United States: (1) fetal fibronectin and (2) salivary estriol. The presence of a positive fetal fibronectin test in the midtrimester of pregnancy is strongly associated with early spontaneous preterm birth. In contrast, a positive salivary estriol test is associated with late preterm birth, thus limiting its clinical use. Both tests have low test sensitivity and are currently used clinically for their negative predictive values. That is, women who screen negative are at very low risk for preterm birth and, thus, no interventions are indicated to prevent preterm birth. Women with a positive test are at increased risk and would be candidates for intervention. One of the main limitations of fetal fibronectin and salivary estriol, and an array of other proposed markers, is the fact that while these markers may aid in identification of women at increased risk for preterm birth, the authors currently have no clearly effective obstetric interventions for preterm-birth prevention in these high-risk women. Use of tocolytics, antimicrobials, or progesterone therapy currently has limited or unproven benefit in the management of women deemed at increased risk using these markers. Thus, until effective targeted obstetric interventions are available, the use of biochemical markers to identify women at increase risk for preterm birth remains largely research tools.

Fetal fibronectin: the impact of a rapid test on the treatment of women with preterm labor symptoms

OBJECTIVE

The purpose of this study was to determine whether knowledge of the results of a rapid fetal fibronectin test affects treatment decisions during the evaluation and treatment of possible preterm labor. Previous observational studies have suggested that a negative test might help to avoid unnecessary intervention.

STUDY DESIGN

This was a randomized study of women who were between 24 weeks and 34 weeks 6 days of gestation with symptoms of preterm labor and who were seen in three community hospitals. A rapid fetal fibronectin test was performed on all subjects. Patients were assigned randomly to a group whose results were known to physician or to a group whose results were not known. Treatment decisions were at the discretion of the physician.

RESULTS

One hundred eight samples were collected between September 2000 and December 2001. There were 10 positive fetal fibronectin tests. The overall prevalence of delivery within 2 weeks for the study population was 2.8%. For women who had negative fetal fibronectin test results, the hospital stay was not significantly shorter when the result was known (6.8 hours) than when it was not known (8.1 hours, P =.35). However, when the physician knew the fetal fibronectin status of women with a negative test result who were observed for >6 hours, the hospital stay was shortened 40%, to 22.7 hours from 37.8 hours (P =.04).

CONCLUSION

Fetal fibronectin testing may be able to supplement clinical judgment in the evaluation of the condition of patients with symptoms of preterm labor. The greatest benefit of fetal fibronectin testing might be for the patient whom the physician judges to be at high risk for imminent delivery. In such patients, the knowledge of a negative fetal fibronectin may shorten the hospital stay.

Accuracy of cervicovaginal fetal fibronectin test in predicting risk of spontaneous preterm birth: systematic review

OBJECTIVE

To determine the accuracy with which a cervicovaginal fetal fibronectin test predicts spontaneous preterm birth in women with or without symptoms of preterm labour.

DESIGN

Systematic quantitative review of studies of test accuracy.

DATA SOURCES

Medline, Embase, PASCAL, Biosis, Cochrane Library, Medion, National Research Register, SCISEARCH, conference papers, manual searching of bibliographies of known primary and review articles, and contact with experts and manufacturer.

STUDY SELECTION

Two reviewers independently selected and extracted data on study characteristics, quality, and accuracy.

DATA EXTRACTION

Accuracy data were used to form 2x2 contingency tables with spontaneous preterm birth before 34 and 37 weeks' gestation and birth within 7-10 days of testing (for symptomatic pregnant women) as reference standards. Data were pooled to produce summary receiver operating characteristic curves and summary likelihood ratios for positive and negative test results.

DATA SYNTHESIS

64 primary articles were identified, consisting of 28 studies in asymptomatic women and 40 in symptomatic women, with a total of 26 876 women. Among asymptomatic women the best summary likelihood ratio for positive results was 4.01 (95% confidence interval 2.93 to 5.49) for predicting birth before 34 weeks' gestation, with corresponding summary likelihood ratio for negative results of 0.78 (0.72 to 0.84). Among symptomatic women the best summary likelihood ratio for positive results was 5.42 (4.36 to 6.74) for predicting birth within 7-10 days of testing, with corresponding ratio for negative results of 0.25 (0.20 to 0.31).

CONCLUSION

Cervicovaginal fetal fibronectin test is most accurate in predicting spontaneous preterm birth within 7-10 days of testing among women with symptoms of threatened preterm birth before advanced cervical dilatation.

A perspective on the diagnosis of preterm labor

Over the past few decades there has not been any significant reduction in the rate of preterm birth. As we enter into a new millennium, prematurity is still the leading cause of perinatal morbidity and mortality in the non-anomalous infant. The only major contributions in reducing perinatal mortality in the preterm infant are those in the field of neonatology, while the area of preterm birth prevention has lagged far behind. This article highlights the research and clinical challenges that stand in the way of making a timely yet accurate diagnosis of preterm labor. In addition, possible pathways in the evolution of preterm labor are discussed with emphasis on their significance to diagnosis and treatment.

Treatment of preterm labor

The ultimate goal of treating preterm labor is to prolong the pregnancy long enough to decrease the incidence of neonatal mortality and morbidity associated with prematurity, while minimizing maternal and fetal risks. There are many controversies in treating preterm labor. Much of this controversy stems from the difficulty in establishing efficacy and safety of interventions and uncertainty of the diagnosis of preterm labor. This article outlines conventional measures and tocolytic therapy directed at prolonging the pregnancy. A review of the effect of tocolytic agents, administration, side effects, and nursing interventions is included. Key words: preterm labor treatment,