Cut-off Value of Initial Serum β-hCG Level Predicting a Successful MTX Therapy in Tubal Ectopic Pregnancy: a Retrospective Cohort Study

Objective: To determine the optimal serum β-hCG cut-off level to predict MTX treatment success in tubal ectopic pregnancy (EP).

Study Design: Data of 240 women, who presented between 2003 and 2011 at the Department of Gynecology and Obstetrics, Medical University of Vienna, with tubal EP and who received MTX as primary treatment, were retrieved from the hospital information system (KIS). 198 patients could be included for final evaluation. Statistical analysis included area under the ROC curve, maximal Euclidean and Youden index, chi-squared and a five-fold cross validation.

Results: The serum β-hCG level cut-off value was calculated at 2121mlU/ml with a specificity of 76.54% and sensitivity of 80.56% (AUC 0.789; p<0.001). Patients with an initial serum β-hCG level below 2121mlU/ml (n=131) experienced MTX treatment failure in 5.3% (n=7), compared to 43.3% (n=29) of patients with an initial serum β-hCG level equal to or above 2121mlU/ml (n=67). There was no statistically significant correlation between clinical symptoms and the MTX therapy outcome (p=0.580; likelihood quotient p=0.716).

Conclusion: The correct decision of therapy in patients with tubal ectopic pregnancy still represents a challenge. In this study we can conclude that, according to our results there is no endpoint of initial serum β-hCG levels, which can be clearly used as cut-off value for the optimal management of tubal EP. However, an initial serum β-hCG level of less than 2121mlU/ml seems to be a good value to expect a successful MTX treatment. Limitations are the retrospective study design and the inability of classifying clinical symptoms like pain as an objective parameter. Wider implications of the findings may include more detailed patient information and more accurate selection of suitable patients for MTX therapy.