Falling in serum β human chorionic gonadotropin levels between days 1 and 7 as a new protocol to predict successful single-dose of methotrexate therapy for ectopic pregnancy

ObjectiveTo study the patterns of serum βhCG levels on days 1–4 and days 1–7 after single-dose methotrexate injection (MTX) for ectopic pregnancy (EP) and to determine the sensitivity, specificity, positive (PPV) and negative predictive values (NPV) of the best cut-off points for the “percentage of fall” in serum βhCG levels for predicting a successful outcome.Patients and methodsThis is a retrospective cohort study including forty-nine consecutive patients treated with single-dose MTX (50 mg/m2). We analyzed patterns of falling in βhCG levels on D1, D4 and D7 of follow up. Our main outcome measures included the overall success rate, the “percentage of fall” variable of serum βhCG levels on D4 and D7 and the best cut-off point for the “percentage of fall” that predicts a successful outcome.ResultsThe success rate of single-dose MTX treatment in EP was 77.5%. A cut-off “percentage of fall” in βhCG serum levels on D1–D7 of ⩾33% has the best sensitivity (96%) and PPV (85%) for predicting a successful outcome. This is out performing any cut-off on days 1–4 and comparable to the standard D4–D7 protocol.ConclusionsAfter single-dose MTX injection for EP, the use of D1 to D7 follow up protocol outperforms that of D1 to D4; with possible elimination of D4 routine βhCG blood draw. A cut-off “percentage of fall” in βhCG serum levels on D1–D7 of ⩾33% has the best sensitivity and PPV.