Suspected ectopic pregnancy. What to do when human chorionic gonadotropin levels are below the discriminatory zone.

OBJECTIVE: To assess the value of a noninvasive diagnostic strategy in cases of suspected ectopic pregnancy when transvaginal sonography (TVS) and serum human chorionic gonadotropin (hCG) measurement show inconclusive findings.

STUDY DESIGN: Prospective study of 85 patients without pregnancy detectable on initial TVS together with low hCG levels (< 1,500 IU/L). The diagnostic strategy combined the results of TVS, hCG measurements and time, according to a strict algorithm.

RESULTS: Overall test results of the strategy were excellent: sensitivity, 0.94; specificity, 1.00; likelihood ratio of a positive test result, infinity; likelihood ratio of a negative test result, 0.06. The strategy revealed a new diagnostic entity, trophoblast in regression (TIR). TIR represents patients with declining hCG levels and unknown locations of their pregnancies, presenting a benign clinical picture, and constituted 54% of the population studied.

CONCLUSION: This noninvasive diagnostic strategy proved to be very reliable. Because the strategy integrated expectant management of patients with declining hCG levels, it prevented many unnecessary surgical procedures. This was of great benefit for both patients with early intrauterine pregnancies and those with TIR.