Do the change in β-hCG values between the 0th and 4th day in tubal ectopic pregnancy treatment with a single-dose methotrexate (MTX) protocol, predict the need for a second dose of MTX?

Aim: The single-dose methotrexate (MTX) regimen is effective and minimizes side effects but an additional 2nd dose is needed in case of failure in an ectopic pregnancy (EP). We aimed to predict the additional MTX dose by evaluating the change in β-hCG values between day 0 and day 4 in EPs with administered single-dose MTX regimen. Method: A total of 454 tubal EPs between 2013 and 2019 were evaluated retrospectively. Cases cured with a single dose of MTX without an additional dose were accepted as the control group, and cases under a single-dose regimen were cured by applying a second dose of MTX on the 7 th day were accepted as the study group. Obstetric and demographic characteristics and the change in β-hCG values compared in both groups. Results: : Age, body mass index (BMI), gravida, smoking, abdominal surgery, presence of IUDs, initial β-hCG levels (0 th day), and EP size were similar in both groups, but the presence of previous EP history was significantly higher in the study group. The change of β-hCG from days 0 and 4 determined that a 20% increase predicts the need for a 2nd dose of MTX with 72.4% sensitivity, and 87.8% negative predictive value (NPV). Conclusion: The single-dose MTX protocol is successful in 83.3% of convenient cases (as the control group), but, an increase of 20% in β-hCG between days 0 and 4 predicts the patients that need to be administered 2nd dose MTX, and thus, a double-dose MTX protocol will be achieved early.