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Ratio of AFP in vaginal blood to maternal serum is a marker for pregnancy failure
Clinical Question
Can the ratio of alpha fetoprotein (AFP) in vaginal blood to AFP in maternal serum confirm pregnancy failure?
Bottom line
For threatened miscarriage, an alpha fetoprotein (AFP) concentration ratio in vaginal blood to maternal serum of more than 13.4 was 100% specific to confirm pregnancy failure. Ratios between 4.3 and 13.4 were equivocal, and ratios less than 4.3 were reassuring. This assessment can be made the same day as the bleeding incident occurs, reducing the wait time for reassessment based on maternal serum beta-HCG levels. This should be considered a proof of concept study; replication in additional and larger samples is needed before wide-spread adoption. 2b
Reference
Study design: Diagnostic test evaluation
Funding: Foundation
Setting: Outpatient (specialty)
Synopsis
Women were included in this diagnostic test evaluation if they had a single intrauterine pregnancy, confirmed by transvaginal ultrasound, and vaginal bleeding. Although gestational ages were not provided, these would presumably be first trimester to early second trimester pregnancies. AFP was measured in vaginal blood and maternal serum from samples obtained within 1 hour of each other. The ratio of vaginal AFP to maternal serum AFP was calculated for each woman. Four groups of women were evaluated: missed or incomplete miscarriage with cervical dilation and no fetal cardiac activity (n = 30), threatened miscarriage with fetal cardiac activity (n = 15), women who underwent cerclage as control patients without pregnancy loss (n = 9), and women undergoing dilation and curettage with confirmed (viable or nonviable) intrauterine pregnancy as control patients with pregnancy loss (n = 22). The authors constructed standard receiver operating characteristic curves plotting sensitivity percentage against 100 minus specificity. They found that at a cut-off ratio of vaginal blood to maternal serum of 4.3 there was 100% sensitivity and 87% specificity for detection of fetal tissue. At a cut-off of 13.4 there was 100% specificity and 73% sensitivity for detection of fetal tissue.
Reviewer
Linda Speer, MD
Professor and Chair, Department of Family Medicine
University of Toledo
Toledo, OH
Comments
It would have been relevant for me when I miscarried as I wanted to be sure the pregnancy was not viable before anything else was done.
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Excellent