Role of day 4 HCG as an early predictor of success after methotrexate therapy for ectopic pregnancies.

OBJECTIVE: To validate whether change in serum HCG levels between days 0 and 4 confer any prognostic value during methotrexate therapy and to quantify its change.

STUDY DESIGN: This is a retrospective study of 48 tubal ectopic pregnancies treated with single dose methotrexate protocol at University Hospital, Muscat, Oman from January 2012 to December 2013. The clinical outcome was analyzed based on the complete resolution of HCG levels or need for additional doses of methotrexate or recourse to surgery. The percentage change in HCG levels between days 0 and 4 (HCG index) of methotrexate were calculated and receiver operator characteristics curve was plotted to identify the best cutoff levels. In order to get a robust 95% confidence interval, bootstrap method using R software was done using 1000 re-sampling. ROC curve and the predictive values were estimated using MEDCALC software.

RESULTS: The mean HCG level on day 4 is significantly higher in treatment failure group (4254±4095 IU/L vs. 2109±3646 IU/L, P=0.008). The HCG levels between day 0 and 4 decreased in 42.7% (21/48) of cases and 80.9% of these cases had treatment success. The HCG levels increased in 57.4% (27/48) of cases and 33.3% of these cases had treatment success. (P=0.001). A 10 percent decline in day 4 HCG levels predict the treatment success with sensitivity of 77% and Specificity 81%. The area under the ROC curve was 0.82 (95% CI: 0.67-0.92), (P<0.001).

CONCLUSION: The success with single dose of methotrexate therapy for tubal ectopic pregnancies was predicted early in the course of treatment by following three key findings: the absolute mean HCG values on day 4, decrease in HCG level from day 0 to 4 and 10% or more fall in day 4 HCG levels.