Abstract
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.
Acknowledgments
The authors thank all the members of the IFCC (International Federation of Clinical Chemistry) Working Group for Standardization of hCG and those of the International Society for Oncodevelopmental Biology and Medicine (ISOBM) Tissue Differentiation (TD)-7 Workshop on hCG Measurement. Special thanks to U-H Stenman for advice and W Merz for continuous collaboration and critically reading the manuscript. Hormones and hormone variants were kindly supplied by the IFCC, the National Institute for Biological Standards and Control (NIBSC) and by K Mann and R Hörmann. N Sampson provided editorial help. The skilled technical assistance of R Gerth is highly appreciated. The Austrian Science Fund (NFN S9307-B05) in part supported the work of P Berger.