Test Strips Identify Fetal Tissue in Vaginal Blood

Marcia Frellick

November 10, 2022

A rapid test strip can accurately identify embryonic or fetal tissue in vaginal blood at the bedside, say authors of a paper published in Obstetrics and Gynecology.

The strip, called the ROM Plus test, can detect alpha-fetoprotein (AFP) and insulin-like growth factor–binding protein 1 (IGFBP-1) to identify the presence of the tissue, researchers say.

A positive test could help diagnose miscarriage and rule out ectopic pregnancy.

The ROM Plus test was originally created for diagnosing rupture of amniotic membranes and has been approved by the Food and Drug Administration. This study describes an off-label use of the test.

Lead author Michelle Volovsky, MD, of the department of obstetrics and gynecology at Maimonides Medical Center in Brooklyn, N.Y., said that in the current legal climate for abortion care, the test could have an additional use for women having vaginal bleeding.

"This test could be used as evidence to confirm that a miscarriage has occurred, and hence, a D&C (dilation and curettage) procedure in that case is not an induced abortion of a viable pregnancy," Volovsky said.

Women in Study

Three groups of reproductive-age women (totaling 90) were included in the study.

One was a negative control group consisting of nonpregnant women undergoing D&C or experiencing vaginal bleeding (n = 23). The positive control group of women had confirmed intrauterine pregnancy undergoing D&C (n = 31), and the third group was a study group of pregnant women with first-trimester bleeding (n = 36). Twelve women in the study group had confirmed ectopic pregnancies.

High Sensitivity and Specificity

Overall, 47 women had confirmed embryonic or fetal tissue in vaginal or uterine blood samples. The test strip was accurately positive in 45 of those 47 cases for a test sensitivity of 95.7%. The other 43 had confirmed absence of embryonic or fetal tissue in their vaginal or uterine blood samples.

The test had high specificity as well. "In the absence of embryonic or fetal tissue, such as vaginal blood sampled in cases of ectopic pregnancy, threatened or complete miscarriage, or nonpregnant individuals, the test strip had a specificity of 97.7% for obtaining a negative result," the authors wrote.

The researchers noted that the high sensitivity and specificity were seen as all tests were performed in real-time, common clinical scenarios encountered in a high-volume, urban Ob/Gyn unit.

First-Trimester Bleeding Can Be Common

First-trimester bleeding occurs in 20%-40% of pregnancies and results in almost 500,000 emergency department visits in the United States every year, the authors wrote.

The most common causes include threatened miscarriage, but more serious etiologies include ectopic pregnancy.

Because criteria often are not met for ectopic pregnancy, many women are told they have a pregnancy of unknown location, which can lead to extensive and expensive follow-up.

"The current study was designed to offer a simple diagnostic alternative that does not require the use of an automated laboratory analyzer," the authors wrote.

The test could be used by patients with confirmed intrauterine pregnancies at home – a highly desirable feature for people hesitant to come into medical offices or who live in remote areas, they noted.

Questions About Test's Use

Lauren Thaxton, MD, assistant professor in the department of women's health at the University of Texas at Austin, told this publication she sees the ease of use by patients at home as the biggest benefit of the test strips.

She said she's not sure they would add much benefit otherwise because "we already have a pretty great way of identifying pregnancy tissue by floating the products of conception."

She said the traditional "floating products" method is very inexpensive, involving a pan and strainer, and may be more comprehensive in that it can determine whether a miscarriage is finished.

She also wonders whether in the current legal climate of abortion laws, the test could be used not only to prove that an abortion didn't happen but used as evidence the opposite way to criminalize abortion.

It's unfortunate that we are evaluating new technology as 'could this cause more harm than good?' But I think it would be wrong not to recognize the long history of criminalization of abortion as well as the current reproductive health and policy climate," Thaxton said.

Coauthors Amir Mor, MD, PhD, and Hugh Taylor, MD, hold U.S. patent rights related to the methods described in this article. Coauthor David Seifer, MD, received payment from the Women's Integrated Network and Rutgers Medical School. In this article the authors describe off-label use of the ROM Plus test kit, produced by Laborie USA. This device was used to test vaginal blood for the presence of embryonic or fetal products. The other authors did not report any potential conflicts of interest. Thaxton reports no relevant financial relationships.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.


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