βhCG monitoring after single-dose methotrexate treatment of tubal ectopic pregnancy: is the Day 4 βhCG necessary? A retrospective cohort study.

Background: In ectopic pregnancy (EP) management, failure of βhCG to fall more than 15% between Days 4 and 7 after methotrexate administration indicates the need for a second dose. Regimens preferring a 25% fall in βhCG between methotrexate administration and Day 7 have been proposed.

Aims: Our study analysed these and other regimens' performance in predicting treatment success. Secondarily, we investigated how each regimen guided the prescription of additional methotrexate doses.

Methods: Medical files of 88 women with ultrasound confirmed tubal EP and pretreatment βhCG <6000 IU/L, unsuitable for expectant management, were retrospectively analysed. The βhCG monitoring regimens studied were (i) 15% fall Day 4-7, (ii) 25% fall Day 0/1-7, (iii) any fall Day 0/1-7, (iv) any fall Day 0/1-4 and (v) 20% fall Day 0/1-4. Treatment success was defined if the EP resolved without surgical intervention. Statistical analysis was performed using McNemar's test.

Results: Overall, treatment success with methotrexate was 92% (n = 81/88). Predicting success of methotrexate (PPV 98-100%) and detecting those needing surgery (specificity 86-100%) were equivalent across all monitoring regimens. However, the 25% Day 0/1-7 fall (and the Day 0/1-4 regimens) over-selected women for a second dose of methotrexate (P < 0.05).

Conclusion: The performance of each regimen is equivalent to the traditional 15% fall Day 4-7 regimen in predicting treatment success. However, a regimen aiming for a 25% fall in βhCG Day 0/1-7 over-selects patients for a second methotrexate dose. In comparison, any drop in βhCG Day 0/1-7 does not over-select women and eliminates Day 4 testing.