J Reprod Med
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Case Reports
Limitations of qualitative serum beta-HCG assays in the diagnosis of ectopic pregnancy.
Seventy-four patients had ectopic pregnancies proven by surgery. Three of them had a serum beta-HCG test for pregnancy that was reported as negative (less than 25-35 mIU/ml). We sought a threshold for positive in the serum beta-HCG test that would maximize its usefulness in diagnosing ectopic pregnancy. ⋯ Lowering the threshold for positive from 25-35 to 10 mIU/ml might increase the test's sensitivity without sacrificing specificity but would still not ensure detection of all ectopic pregnancies. Of 445 cases of ectopic pregnancy described in the literature, 6 had serum beta-HCG values reported as negative. In the published reports and in our own cases, clinical histories and histologies indicated that a nonviable ectopic pregnancy can be expected to have an associated serum concentration of beta-HCG that may be below the sensitivity of detection even with current, commercially available quantitative tests.