Level B recommendations. None specified.

Level C recommendations. Perform or obtain a pelvic ultrasound for symptomatic pregnant patients with a b-hCG level below any discriminatory threshold.

In cases where the b-hCG level is below a discriminatory threshold, some clinicians may not perform an ultrasound because they believe that the diagnostic utility of pelvic ultrasound is low. In some settings, the emergency physician may be unable to obtain a comprehensive ultrasound in the radiology department for the same reason. However, studies reviewed for this clinical policy showed that the ultrasound may be diagnostic even if b-hCG is below 1,000 mIU/mL. Clinicians may also defer an ultrasound when the b-hCG is low, under the assumption that this correlates with a small embryo and low risk of tubal rupture if the pregnancy is, in fact, ectopic. However, rupture has been documented at very low b-hCG levels and there is a potential harm in deferring ultrasound imaging. Therefore, this policy recommends that a pelvic ultrasound be performed or obtained for symptomatic patients with a b-hCG level below any “discriminatory threshold.” Because the evidence is taken from Class II and III studies, this is a Level C recommendation.

Question 2: In patients who have an indeterminate transvaginal ultrasound, what is the diagnostic utility of b-hCG for predicting possible ectopic pregnancy?

Level A recommendations. None specified.

Level B recommendations. Do not use the b-hCG value to exclude the diagnosis of ectopic pregnancy in patients who have an indeterminate ultrasound.

Level C recommendations. Obtain specialty consultation or arrange close outpatient follow-up for all patients with an indeterminate pelvic ultrasound.

A majority of patients who have a pelvic ultrasound during their ED evaluation for symptomatic early pregnancy will receive a diagnosis of an intrauterine pregnancy or an abnormal pregnancy (e.g., ectopic or molar, fetal demise). A significant minority, however, (approximately 25%) will have an indeterminate (or nondiagnostic) ultrasound. This rate depends on a number of factors, including the clinical setting, patient characteristics, ultrasound machine and operator, and diagnostic criteria used.

Indeterminate ultrasounds pose a management dilemma for the clinician. In order to answer the critical question above, the authors reviewed studies reporting the initial b-hCG level in patients with a final diagnosis of ectopic pregnancy who have an initial indeterminate ultrasound. Positive and negative likelihood ratios for risk of ectopic pregnancy above and below different b-hCG levels were calculated by the authors from the available data.

Nine Class II studies and five Class III studies examined this issue. Likelihood ratios were variable across studies and generally neither high nor low enough to help with clinical decision making. This suggested that the initial b-hCG cannot be used to exclude the diagnosis of ectopic pregnancy and resulted in Level B and Level C recommendations.

Question 3: In patients receiving methotrexate for confirmed or suspected ectopic pregnancy, what are the implications for ED management?

Level A recommendations. None specified.