EP21.26: A novel clinical tool for predicting methotrexate treatment success in ectopic pregnancy

To evaluate clinical factors prior to methotrexate (MTX) treatment for tubal ectopic pregnancy, and to apply the data to a prediction model for treatment success. This is a retrospective study of data recorded in a single tertiary medical centre during 2014-2022. Of 1,040 women with available data who presented with an ectopic pregnancy, 808 presented with a tubal ectopic pregnancy. Among them, 372 with a β-hCG level less than 5000 IU/L were treated with a single dose of 50 mg/m2 MTX and were included in this study. Pretreatment factors including patient characteristics, gestational age, initial β-hCG level, and sonographic parameters were compared between those who achieved complete resolution with the protocol and those who needed either an additional MTX dose or surgical intervention. A logistic regression model and multivariable analysis were employed to predict success. A graphic nomogram was generated to represent the logistic regression model. Complete resolution of the ectopic pregnancy was achieved in 290 women (77.9%). A second dose of MTX or surgical intervention was required for 82 (22.0%): 49 (13.2%) received a second dose of MTX and 33 (8.9%) underwent laparoscopic salpingectomy. Based on significant variables identified by the multivariable logistic regression, the predictive model encompasses initial β-hCG concentration and the visibility of a yolk sac or fetal pole. Analysis with cross-validation techniques revealed that the model was both accurate and discriminative. A predictive nomogram incorporating three variables that are ascertainable during the initial assessment of tubal ectopic pregnancy was developed for predicting the success of single-dose MTX treatment. The nomogram provides a personalised graphic tool to aid clinicians in decision-making.