Human chorionic gonadotropin isoforms and their epitopes: diagnostic utility in pregnancy and cancer.

BACKGROUND Clinical management of pregnancy, pregnancy-related disorders and trophoblastic tumors is dependent on immunoassay measurements of the complex analyte human chorionic gonadotropin (hCG). Differences in hCG results using different methods affect clinical interpretation with potentially adverse consequences for patient care. Objectives/method: To provide an overview of factors contributing to method-related differences in hCG measurements and how to overcome these drawbacks. RESULTS/CONCLUSION Six recently established highly purified and molar unit calibrated World Health Organization Reference Reagents for important hCG variants provide means for in-depth characterization of diagnostic immunoassays for hCG. For different clinical applications in pregnancy and cancer, appropriate epitopes and specificities of pairs of monoclonal antibodies against hCG in immunoassays have been clearly defined. This led to the conclusion that in routine clinical situations assays are preferred that measure all relevant hCG variants. The adoption of new nomenclature unambiguously describing what is being measured and the anticipated introduction of a new highly pure international standard for hCG represent significant progress towards improved analytical reliability and comparability of diagnostic hCG results.