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Q&A |
| The first 300 words of the full text of this article appear below. |
Within the last year, human chorionic gonadotropin (hCG)2 has been a topic of great discussion in both the scientific and popular press. Recent reports have demonstrated that because of hCG’s heterogeneity, assay standardization is an important problem, with different immunoassays giving different results for the same specimens. In addition there have been reports of false-negative results due to high concentrations of certain hCG variants. Finally, the popular press has reported on illicit use of hCG by athletes for performance enhancement and by dieters for weight loss. In all, these publications raise questions about what variants of hCG are currently being measured, what should be measured, and how best to do it. In this Q&A article, 5 leaders in the field have been asked to comment on current clinical assays for hCG and what the future might hold.
There has been a lot in the literature lately about the lack of standardization of hCG immunoassays. The data suggest that in most cases we don’t know what hCG variants our immunoassays are measuring. What are the most immediate changes that you feel need to be made to hCG immunoassays regarding standardization?
Catharine Sturgeon3 : I think it is really important that laboratories know the specificity of the method used as the specificity needs to be different for pregnancy and cancer applications. It’s important to know the extent to which different hCG variants are recognized in different methods. The highly purified WHO International Reference Reagents (IRR) for 6 hCG-related isoforms, which were produced by the IFCC Working Group for hCG, now enable manufacturers to characterize the extent to which their immunoassays measure those important isoforms. Reaching consensus about how best to assess this, as well as how to present the data so as to allow easy comparison of methods, will represent a major step forward. Studies to assess the influence of calibrator purity on results are also in progress. Thankfully, we can now describe the major variants using the systematic and user-friendly nomenclature developed by the IFCC Working Group. We all need to work hard to encourage its universal adoption.
Since the IRR are calibrated
Do you feel that, along with hCG results, laboratories should report which hCG variants their assay measures?
hCG has been in the popular press lately because of illicit use by athletes, and as adjunct to fad diets. Have you seen this type of hCG use and do you feel that the hCG assays we have available today have the limits of quantification and specificity to detect illicit hCG use?
What do you think the future holds for hCG methods? Do you think that immunoassay methods will give way to mass spectrometry–based methods?
What are some of the limitations to measuring hCG by mass spectrometry?
Qualitative urine hCG immunoassays also suffer from lack of standardization. In addition, they are subject to false-negative results when certain hCG variants are present in excess. Given their limitations, do you think that qualitative assays are still clinically useful?
Which hCG variants do you think quantitative immunoassays should be able to detect? Do you think that assays should be designed and marketed for specific uses such as to detect pregnancy vs as a tumor marker vs as a marker of gestational trophoblastic disease?
Do you have any additional comments?
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