Single Serum Activin A Testing to Predict Ectopic Pregnancy

Abstract

Ectopic pregnancy (EP) is an important cause of maternal deaths in early pregnancy because most fatal cases result from delayed diagnosis and inappropriate investigation. We evaluated whether the measurement of activin A may be useful in the diagnosis of EP in women with unknown pregnancy location. The study was designed as an open observational study. The study was set in a tertiary referral center for obstetric care. Patients were women with unknown pregnancy location (n = 536) who had complaints of bleeding, pain, or cramping. Interventions included clinical examination; transvaginal ultrasound scan; human chorionic gonadotropin (hCG), progesterone, and activin A measurements; laparoscopy; uterine curettage; and histological examination. Main outcome measures were pregnancy outcomes and evaluation of sensitivity, specificity, and predictive values of hCG, progesterone, and activin A as diagnostic tests for the detection of EP. Pregnancy outcomes included 155 (28.9%) viable intrauterine pregnancies (IUP), 305 (56.9%) first-trimester spontaneous abortion (SAB), and 76 (14.2%) EP. SAB had the lowest (P < 0.0001) hCG and progesterone concentrations, significantly lower than EP (P < 0.001) and IUP (P < 0.001). In EP, levels were significantly (P < 0.001) lower than in IUP. On the contrary, activin A levels were lowest (P < 0.0001) in EP, significantly lower than in SAB (P < 0.001) and IUP (P < 0.001). IUP had significantly (P < 0.001) lower activin A levels than SAB. When evaluated by the receiver operating curve analysis, activin A at the cutoff of 0.37 ng/ml combined a sensitivity and a specificity of 100 and 99.6%, respectively, for prediction of EP. When activin A concentrations were below the cutoff, the positive predictive value for EP was 97.43%, and 0% for concentrations higher than 0.37 ng/ml. Activin A measurement may identify patients at risk of EP with a high sensibility and specificity.