Urgent message: Ectopic pregnancy must be considered in women of childbearing age who present with abdominal pain—even if ‘ruled out’ by a negative hCG test. Show Yi-An A. Lee, MD, MPH, Gino Farina, MD, and Helene Lhamon, MD Standard urine hCG tests are able to detect ß hCG levels as low as 20 mIU/mL. This case report shows that an ectopic pregnancy can exist and be large enough to rupture at ß hCG levels below the threshold detectable by urine pregnancy screening tests. Considering the mortality and morbidity associated with a ruptured ectopic pregnancy, this case report emphasizes the necessity of confirming a negative serum quantitative hCG before ruling out ectopic pregnancy. Introduction Standard urine hCG tests are able to detect ß hCG levels as low as 20 mIU/mL. This case report shows that an ectopic pregnancy can exist and be large enough to rupture at ß hCG levels below the threshold detectable by urine pregnancy screening tests. Considering the mortality and morbidity associated with a ruptured ectopic pregnancy, this case report emphasizes the necessity of confirming a negative serum quantitative hCG before ruling out ectopic pregnancy. [Note: While this case report concerns a patient who presented in an ED setting, abdominal pain is a common presenting complaint in urgent care. The teaching points are highly relevant to the urgent care practitioner.] Case Report She described the pain as 10 out of 10 in severity (i.e., the worst pain imaginable in the patient’s estimation); the pain was greatest in the left lower quadrant, and became worse with any motion. The review of systems was pertinent for the presence of vaginal spotting and right shoulder pain, and for the absence of chest pain, shortness of breath, syncope, or fever. The patient’s past medical history was significant for infertility, fibroids, and irregular menses. She had no prior surgical history, took no medications, and had no allergies. She had no risk factors for ectopic pregnancy: no history of sexually transmitted diseases or pelvic inflammatory disease, no prior gynecological surgery, no intrauterine device use, and she was not taking fertility medications. Her initial vitals were as follows:
The patient was clearly uncomfortable, but not in acute distress. Cardiac exam revealed a regular rate and rhythm. Pulmonary exam was clear to auscultation bilaterally. Abdominal exam revealed positive bowel sounds, soft without guarding but extremely tender to palpation, with diffuse rebound and a positive pelvic shake. Pelvic exam was notable for cervical motion tenderness and bilateral adnexal region tenderness; uterine and adnexal size were difficult to assess secondary to pain. The urine hCG was negative. Intravenous access was obtained, and a complete blood count, chemistry panel, blood type and cross, and serum quantitative hCG were sent to the laboratory. The patient was given intravenous fluids and the ob/gyn service was promptly consulted. The ob/gyn physician performed a bedside ultrasound, which showed free fluid and a left adnexal mass; the patient was taken immediately to the operating room with the
presumptive diagnosis of a ruptured hemorrhagic ovarian cyst. Discussion Four theoretical mechanisms have been proposed to explain unusually low or undetectable ß hCG levels in ectopic pregnancies:2
A negative urine hCG does not definitively rule out ectopic pregnancy, regardless of the date of the last menstrual period. If suspicion of pregnancy exists, a serum quantitative ß hCG should be obtained. An article by Brennan notes that 10% of ectopic pregnancies with a quantitative ß hCG <100 mIU/mL were ruptured, and that 7% of all ectopic ruptures occurred at levels <100 mIU/mL.3 It is commonly accepted that
one should not expect to see ultrasonographic findings consistent with an intrauterine pregnancy with a quantitative ß hCG of less than 1200 mIU/mL.5 However, this discriminatory threshold does not apply to ectopic pregnancies; it would be a dangerous error to forego ultrasound to rule out an ectopic on the basis of a low serum hCG. One study demonstrated that 56% of ectopic pregnancies confirmed by ultrasound had serum hCG levels below 500 mIU/mL.6
Conclusion REFERENCES
Can you have an ectopic pregnancy with negative pregnancy test?Although hCG is still produced during ectopic pregnancy, the levels of this hormone are lower and harder for a pregnancy test to pick up than in a regular pregnancy. For this reason, 1% of ectopic pregnancies will have a negative pregnancy test result.
Is ectopic pregnancy visible on pregnancy test?Would an Ectopic Pregnancy Show Up on a Home Pregnancy Test? Since ectopic pregnancies still produce the hormone hCG, they'll register as a positive home pregnancy test. People with ectopic pregnancies will also experience early pregnancy symptoms like sore breasts, nausea, spotting, and more.
How soon would you know if you have an ectopic pregnancy?Symptoms of an ectopic pregnancy usually develop between the 4th and 12th weeks of pregnancy. Some women don't have any symptoms at first. They may not find out they have an ectopic pregnancy until an early scan shows the problem or they develop more serious symptoms later on.
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