Threatened Preterm labor (TPL) accounts for 1,000's of unnecessary yearly admissions with an average cost of $14,000 per patient. With a 98% specificity, Fetal Fibronectin (FFN) is a very powerful test that can safely rule out threatened preterm labor with nearly 99% accuracy for up to two weeks. However the company states that a “recent vaginal examination” is a contraindication as it may lead to a false positive. Yet they submit no clinical research to support this statement.
Two FFN sampling were collected from 18 patients whom met the indicated criteria for TPL. Criteria included single gestation between 24–33 6/7 weeks, no sexual intercourse or vaginal exam within past 48 hours, or showing signs or symptoms of preterm labor. Patients were initially sampled for FFN, vaginal exam performed, following a second FFN sampling was collected. The two samples were then compared against each other and patients were followed until they went into labor.
Of the 18 patients, (14) patients tested FFN neg/neg. (2) positive/neg, (1) neg/positive and (1) positive/positive, Of 15 initial neg results, only one tested positive after vaginal exam, yielding a 6% false positive. Of three who tested initially positive, two retested neg, Neither delivered before 37 weeks.
Though a small sample size, study shows “recent vaginal exam” prior to FFN sampling yields a very low rate for false positives and should no longer be considered a contraindication to testing. Furthermore with an initial positive test result, a repeat test should be performed for true negative.
Wyckoff Heights Medical Center, New York, NY
Financial Disclosure: The author did not report any potential conflicts of interest.