Lowered reference limits for hCG improve follow-up of patients with hCG-producing tumors

Abstract

BackgroundHuman Chorionic Gonadotropin (hCG) is produced by germ cell tumors, but can also be elevated in benign conditions such as primary hypogonadism, where hCG is produced by the pituitary gland. In our experience, the reference limits for hCG (Elecsys hCG+β-assay, Roche Diagnostics), were unnecessarily high and did not reflect levels encountered in clinical practice. We wanted to establish new reference limits to increase the clinical utility of the hCG-assay. MethodsWe analysed hCG in serum samples from a healthy adult population and in a cohort of testicular cancer survivors. The gonadotropins LH and FSH were measured in the cohort and in a selection of the reference population to assess gonadal function. ResultsWe found low hCG levels for all men and women <45years (97.5 percentiles 0.1 and 0.2IU/L, respectively) from the healthy population (n=795) having normal FSH and LH. Due to assay limitations, we suggest a common reference limit of <0.3IU/L. For the age group ≥45, the 97.5 percentiles in the healthy population were 0.5IU/L for men and 6.0IU/L for women. In all subjects from both the reference population and the cohort (n=732), hCG levels exceeding the reference limit could be fully explained by reduced gonadal function indicated by elevated LH and FSH levels. ConclusionThe Elecsys hCG+β-assay should have lower reference limits than recommended by the manufacturer, with important implications for tumor follow-up. Elevated hCG is rare with intact gonadal function, both in a normal population and among survivors of testicular cancer, and should lead to further investigations when encountered in clinical practice.