Abstract
This study questions whether hCG results correctly reflect the concentration and forms of hCG that exist in the circulation. Common analytical platforms used in this study included those from Abbott, Vitros, Siemens, Beckman Coulter, Roche and Dade Behring. These immunoassay platforms are commonly used to measure hCG forms, including intact hCG, total β-hCG (intact hCG and hCG-free β-subunit) and/or hCG-free β-subunit.
The study was organized by a proficiency testing programme in response to the Waddsworth Center of the New York State Department of Health recommendations. hCG-free human serum matrix was spiked with various concentrations of either β-hCG or intact hCG. Samples were delivered to 266 laboratories in the United States. The authors found that 9.3% of laboratories measuring intact hCG reported it as total β-hCG; conversely 13.1% of laboratories measuring total β-hCG reported it as intact hCG. The occurrence of such errors is likely to be a problem worldwide.
The authors highlight the impact of these erroneous results, reporting on the clinical role of hCG in the diagnosis and monitoring of conditions such as ectopic pregnancy, trophoplastic gestational diseases, choriocarcinoma and testicular cancer. The complexity of the hCG molecule, confusion with hCG nomenclature and the lack of information regarding assay specificity provided by manufacturers are thought to be the main reasons for the incorrect reporting of results. Reaching a consensus on nomenclature and the availability of a World Health Organization reference material for hCG will help resolve some of these issues. However, there is an urgent need for manufacturers to clearly state what forms of hCG are detected by their assays and for laboratories to share this information with their clinical service users.