Bedside Test to Rule out an Ectopic Pregnancy Using a Modified Fda Approved Kit

Volovsky, M.; Duarte, M. G.; Taylor, H. S.; Mor, A.

Objective: To evaluate the accuracy of a modified bedside test in ruling out an ectopic pregnancy. The test is based on a lateral flow immunoassay for alpha-fetoprotein (AFP). It has been shown that a high AFP level in vaginal blood indicates the passage of fetal tissue, suggestive of a miscarriage [1]. We hypothesized that high AFP levels in sampled intrauterine tissue, assuming non-heterotopic pregnancy, rules out the presence of an ectopic pregnancy. Materials and Methods: This is a prospective cohort study. The study included pregnant women undergoing a dilation and curettage (D&C) for pregnancy loss or termination, women with pregnancy loss or an ectopic pregnancy presenting with vaginal bleeding, and non-pregnant women with vaginal bleeding. Vaginal blood was collected on gauzes, sanitary pads, and cotton swabs. Samples were then tested for AFP levels using a commercial kit (ROMplus, Laborie, USA) originally designed to detect leakage of amniotic fluid. This kit contains a lateral flow immunoassay strip capable of detecting the presence of AFP. Positive samples for AFP were retested at a later date (after 3 to 20 days) to ascertain the stability of AFP and reliability of the test. Official sonograms, pregnancy tests, and final pathology results were obtained to confirm pregnancy status as well as the presence or absence of fetal tissue in the vaginal blood. A sensitivity and specificity analysis was performed against these final results to validate the accuracy of the test strip in ruling out an ectopic pregnancy. Results: A total of 30 vaginal blood samples were tested for AFP. All pregnant women who had a miscarriage or D&C had detectible AFP in their vaginal blood (n=13). On retesting the samples 3 to 20 days later, these results remained the same (positive test strip). The remaining 17 vaginal blood samples were from 4 women with ectopic pregnancies and from 13 non-pregnant women with vaginal bleeding. All 4 ectopic pregnancies had no AFP detected in the vaginal blood and only 1 out of 13 non-pregnant patient samples had AFP detected. The ROMplus test strip correctly detected AFP in all samples tested containing fetal tissue (n=13) resulting in a test sensitivity of 100%. ROMplus correctly identified the absence of AFP in 16 out of the 17 samples lacking fetal tissue, a 94% test specificity. Conclusions: ROMplus has the potential to accurately and reliably detect the presence of AFP, and hence fetal tissue, in vaginal blood samples. This could be a vital non-invasive aid in ruling out an ectopic pregnancy at the bedside (currently off-label use). Furthermore, it could limit the amount of invasive testing and visits needed in cases of pregnancies of unknown location. Impact Statement: In light of the recent COVID-19 pandemic, a simple non-invasive bedside test to rule out an ectopic pregnancy is highly desired given its potential for reducing the number of visits, investigations performed, and personnel involved in the workup of a pregnancy of unknown location. Reference: 1. Mor A, Tal R, Haberman S, Kalgi B, Nasab SH, Minkoff H. Same-day confirmation of intrauterine pregnancy failure in women with first-and early second-trimester bleeding. Fertility and sterility. 2018 Jun;109(6):1060.