Authors' objectives

To determine the value of cervicovaginal foetal fibronectin (FF) as a marker for pre-term delivery.

Searching

MEDLINE (from 1966 to November 1997) and EMBASE (since 1989) were searched for original articles published in the English language. The keywords were listed. In addition, the references from identified articles were checked.

Study selection

Assessment of study quality

The authors did not state that they assessed validity.

Data extraction

The methods used to extract the data were not reported. The following data were extracted: patient inclusion and exclusion criteria; definition of a positive test; the total number of patients and the number of true-positive, true-negative, false-positive and false-negative results for delivery at less than 37 or less than 34 weeks; the total number of fibronectin samples and the number of true-positive, true-negative, false-positive and false-negative results for outcomes of delivery within 7,14, 21 or 28 days of fibronectin sampling. Where these values were not reported, attempts were made to recalculate them from the data reported. The sensitivity and specificity was calculated for each study.

Methods of synthesis

Results of the review

A total of 27 studies were included. The outcomes at less than 37 and less than 34 weeks were evaluated using 3,185 and 2,812 women, respectively. The outcome of delivery within 7, 14, 21 and 28 days after fibronectin sampling were evaluated using 3,613 women, 3,892 women, 3,005 women and 2,700 women, respectively.

Homogeneity (P>0.1) was present in only 8 of the 63 analyses. In no analysis were both the sensitivity and specificity rates homogeneous at this level.

FF as a predictor of pre-term delivery, according to gestation at delivery.

For delivery at less than 37 weeks, the sensitivity was 56% (95% CI: 44, 68) and the specificity 84% (95% CI: 81, 88). For delivery at less than 34 weeks, the sensitivity and specificity were 61% (95% CI: 33, 89) and 83% (95% CI: 75, 91), respectively.

FF as a predictor of pre-term delivery, according to the number of days since sampling.

For delivery within 7 days of sampling, the sensitivity was 76% (95% CI: 57, 96) and the specificity 88% (95% CI: 81, 96). For delivery within 14 days, the sensitivity and specificity were 68% (95% CI: 49, 86) and 89% (95% CI: 83, 95), respectively. Similarly, the sensitivity and specificity were 61% (95% CI: 35, 87) and 91% (95% CI: 87, 96), respectively, for delivery within 21 days and 43% (95% CI: 6, 79) and 93% (95% CI: 87, 98) for delivery within 28 days.

The subgroup analysis failed to reduce heterogeneity amongst the studies.

Authors' conclusions

Among patients with symptoms of pre-term labour, cervicovaginal FF appears to be among the most effective predictors of pre-term delivery.

CRD commentary

The review addressed a clearly defined question and the inclusion criteria were well defined. Relevant details of the included studies were tabulated. The search strategy was limited to two electronic databases, there was no attempt to identify unpublished data, and publication bias was not assessed. In addition, the included studies were restricted to English language publications. Given these limitations it seems likely that relevant studies may have been omitted. No details of the methods used to select the primary studies or extract the data were given. The validity of the primary studies was not assessed. It is therefore difficult to assess the potential impact on the results of biases introduced by flaws in the methodologies of the review or the primary studies.

The methods used to pool the studies were generally appropriate. Statistical heterogeneity was assessed and heterogeneity was investigated through subgroup analyses. Results of the analyses were clearly presented. Apart from the indication of subgroups that included only one study, the number of studies in each subgroup was not reported. It seems likely that these would have been small given the number of subgroups and the small total number of studies. Considerable heterogeneity remained after the subgroup analysis; some discussion of other potential sources of heterogeneity and/or graphical representation in receiver operating characteristic space may have been helpful. The discussion commented on the considerable variation in sensitivity and specificity among the studies, and advised caution when interpreting the results from the subgroup analyses.

The authors' conclusions did not follow from the results, as no data for other predictors of pre-term delivery were presented. From the data presented it might be inferred that a positive FF is useful for predicting pre-term delivery (high specificity). However, the reported sensitivities were poor and their CIs very wide, implying that a negative test could not be used to rule out pre-term delivery. The results of this review should be interpreted with caution in view of the problems highlighted.

Implications of the review for practice and research

Practice: The authors did not state any implications for practice.

Research: The authors considered that there is a need for defining an intervention that actually reduces the rate of pre-term delivery. Predictors of patients at risk may include assessment of cervical effacement and dilation of the internal os, which appears to be a promising predictor of pre-term delivery. The addition of ultrasonographic assessment of the cervix to FF testing may further increase the predictive capacity of the model containing fibronectin alone.

Bibliographic details

Leitich H, Egarter C, Kaider A, Hohlagschwandtner M, Berghammer P, Husslein P. Cervicovaginal fetal fibronectin as a marker for preterm delivery: a meta-analysis. American Journal of Obstetrics and Gynecology 1999; 180(5): 1169-1176. [PubMed: 10329873]

Indexing Status

Subject indexing assigned by NLM

MeSH

Biological Markers /analysis; Cervix Uteri /chemistry; Enzyme-Linked Immunosorbent Assay; Female; Fetus /metabolism; Fibronectins /analysis; Gestational Age; Humans; Immunohistochemistry; MEDLINE; Obstetric Labor, Premature /diagnosis; Pregnancy; Risk Factors; Sensitivity and Specificity; Vagina /chemistry

AccessionNumber

11999001234

Database entry date

30/04/2004

Record Status

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.