Ultrasound reliably predicts success and failure of single-dose methotrexate(Drug information on methotrexate) treatment of ectopic pregnancy, according to research conducted at Boston Medical Center and presented Wednesday at the RSNA meeting.

Results from a retrospective trial of 62 patients, presented by BMC radiologist Dr. Sarah Bixby, indicate yolk sac and fetal heart motion predicted all 17 treatment failures. A yolk sac was identified in 15 of 17 of failed cases, producing a specificity and sensitivity of 88% and 100%, respectively. Fetal heart motion was observed in one patient who failed treatment and was not present in any successful cases.

Methotrexate has been a front-line treatment for ectopic pregnancy since 1992, but the success rate of the single-dose methotrexate therapy varies widely, ranging from 64% to 94%. Although methotrexate does not have significant risks, it can lead to life-threatening complications, including hospitalization and surgery in up to 29% of women receiving the therapy.

Overall, Bixby found that a patient's beta-HCG hormone rate offered the strongest predictor of methotrexate treatment failure. Although the success rate for all 62 patients was 76%, it fell to 50% in patients with beta-HCG values more than 2000, and to 20% in patients with values over 5000.

Nonetheless, the findings of yolk sac and heart motion with transvaginal ultrasound were the surest indications that single-dose methotrexate will not work. They should be listed as exclusion criteria in the procedure's clinical protocol, Bixby said.