A Bedside Test to Detect the Presence of Embryonic or Fetal Tissue in Vaginal Blood

Abstract

OBJECTIVE: To evaluate a rapid bedside test that detects alpha-fetoprotein (AFP) and insulin-like growth factor–binding protein 1 (IGFBP-1) to identify the presence of embryonic or fetal tissue in vaginal blood. METHOD: This was a prospective cohort study. Reproductive-aged individuals were recruited into three groups: a negative control group consisting of nonpregnant individuals undergoing dilation and curettage (D&C) or experiencing vaginal bleeding; a positive control group of individuals with confirmed intrauterine pregnancy undergoing D&C; and the study group of pregnant individuals with first-trimester bleeding. Lateral flow immunoassay strips capable of detecting both AFP and IGFBP-1 were used to test vaginal blood for the presence of embryonic or fetal tissue. RESULTS: Ninety individuals were recruited: 31 in the positive control group, 23 in the negative control group, and 36 in the study group, including 12 individuals with ectopic pregnancies, 16 with active miscarriages, four with threatened miscarriages, and four with complete miscarriages. Vaginal blood from 14 of the 16 individuals with active miscarriages was correctly positive for embryonic or fetal tissue. Vaginal blood from all individuals with ectopic pregnancies, threatened miscarriages, and complete miscarriages was negative for embryonic or fetal tissue. Overall, 45 of 47 individuals with confirmed embryonic or fetal tissue in vaginal blood correctly tested positive using the test strips, a test sensitivity of 95.7% (95% CI 85.5–99.5%). Of the 43 individuals with confirmed absence of embryonic or fetal tissue in their vaginal blood, 42 were correctly negative, a test specificity of 97.7% (95% CI 87.7–99.9%). CONCLUSION: A rapid test strip detecting both AFP and IGFBP-1 can accurately identify the presence of embryonic or fetal tissue in vaginal blood. When positive, this could aid in diagnosing miscarriage and ruling out ectopic pregnancy at the bedside.