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Am J Emerg Med. 2009 Oct;27(8):1019.e5-7. doi: 10.1016/j.ajem.2008.12.023. Epub 2009 Sep 22.

False-positive urine pregnancy test in a woman with adenomysosis.

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Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Department of Laboratory Medicine, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.


We present a case of a 39-year-old woman presenting to the emergency department with persistent vaginal bleeding with myoma and endometrium thickness. The qualitative urine human chorionic gonadotropin (hCG) showed positive result, however, the quantitative serum hCG had negative result. The negative serum hCG result suggests that the false-positive result was not caused by elevated circulating hCG. According to the urine hCG one-step pregnancy device, 1 mg/dL of hemoglobin may not interference the pregnancy result. Nevertheless, we found that the hemoglobin level was 40 mg/dL in the urine specimen. We designed a in vitro experiment to evaluate the effects of hemoglobin on urine pregnancy test. The concentrations of hemoglobin from 5 to 500 mg/dL did not yield a positive urine pregnancy test. On the basis of our findings, the false positive pregnancy test was not caused by hemoglobin. It is important to confirm a suspected false-positive urine hCG test using a quantitative serum hCG test. Although it is not certain the mechanism for false positive reaction in this peculiar sample, the ACON urine hCG one-step pregnancy will occasionally yield a false-positive result in this class of patients.

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