An unusual cause of elevated serum total beta hCG.

Human chorionic gonadotropin (hCG), a heterodimeric hormone consisting of an alpha (alpha) and a beta (beta) subunit, is used as a marker for the diagnosis of pregnancy, congenital defects, and choriocarcinoma. After excluding the common causes of elevated serum hCG, laboratory identification of false-positive or true results assists in guiding clinical management. Options include testing urine for hCG, serum for heterophile antibodies, and serum hCG by different immunoassays. We report the case of a non-pregnant patient with chronic renal failure who had a positive urine hCG test, an elevated serum hCG level by two different assays but normal by a third assay, and persistently elevated serum hCG levels after ruling out the likelihood of heterophile antibodies. The discrepancies were explained by the patient's impaired renal clearance and the molecular forms of hCG that were measured by each assay. This case illustrates the importance of the laboratory's role in understanding the causes of elevated serum hCG.