The potential value of activin B and fibronectin for the triage of pregnancies of unknown location and prediction of first trimester viability

AIM: We have assessed the potential predictive ability of the biomarkers activin B and fibronectin (FN1) alone and when added to established markers for triaging patients as being at low or high risk of ectopic pregnancy (EP). We also assessed their use as predictors of viability at 12 weeks gestation. METHODS: Exploratory secondary analysis of a prospective study including all women classified as a pregnancy of known location (PUL) based on transvaginal ultrasonography between January and December 2007 at the early pregnancy unit of St Georges’ Hospital (London). We used multinomial logistic regression to assess the diagnostic potential of the biomarkers to triage PUL at high risk of complications (EP or persistent PUL), and standard binary logistic regression to predict first trimester viability at 12 weeks. RESULTS: For discriminating high‐risk (n = 16) from low‐risk PUL (n = 93), the area under the receiver operating characteristic curve (AUC) was 0.75 (95% confidence interval 0.60–0.85) for activin B and 0.55 (0.41–0.68) for FN1. Adding activin B to a multinomial logistic regression model incorporating β‐hCG ratio and initial progesterone yielded odds ratios of 0.16 (0.05–0.55) for failing vs high‐risk PUL and 0.29 (0.07–1.19) for intrauterine vs high‐risk PUL and increased the model's AUC from 0.84 to 0.89. At a risk threshold of 5% for high‐risk PUL, sensitivity increased from 84% to 87% and specificity from 48% to 64%. For discriminating viable (n = 28) from non‐viable (n = 81) pregnancies at 12 weeks, both markers had an AUC of 0.54. CONCLUSIONS: Our results suggested that activin B may be a promising marker to improve PUL triage in addition to established markers.