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This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: clinchem.2009.124578v1 55/8/1484    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Google Scholar Articles by Sturgeon, C. M. PubMed PubMed Citation Articles by Sturgeon, C. M.

Differences in Recognition of the 1st WHO International Reference Reagents for hCG-Related Isoforms by Diagnostic Immunoassays for Human Chorionic Gonadotropin

¹ Department of Clinical Biochemistry, Royal Infirmary, Edinburgh, UK; ² Institute for Biomedical Aging Research, Austrian Academy of Sciences, Innsbruck, Austria; ³ Department of Clinical Biology, Institut Gustave-Roussy, Villejuif, France; ⁴ Department of Obstetrics and Gynecology, College of Physicians and Surgeons of Columbia University, NY, NY; ⁵ National Institute of Biological Standards and Control, Potters Bar, UK; ⁶ Research Centre for Reproductive Health, Department of Obstetrics and Gynaecology, University of Adelaide, The Queen Elizabeth Hospital, Woodville, Australia; ⁷ Department of Clinical Chemistry, Helsinki University Central Hospital, Finland.

^aAddress correspondence to this author at: Department of Clinical Biochemistry, Royal Infirmary of Edinburgh, Edinburgh EH16 4SA, United Kingdom. Fax 44-131-242-6882; e-mail C.Sturgeon{at}ed.ac.uk

Background: The 1st WHO International Reference Reagents (IRRs) for 6 human chorionic gonadotropin (hCG)-related molecular variants, highly purified and calibrated in substance concentrations by the IFCC Working Group for hCG, permit experimental elucidation of what commercially available hCG methods measure in molar terms and enable assessment of their fitness for clinical purposes.

Methods: Pools containing known amounts of the IRRs spiked into normal human serum were issued to participants through the UK National External Quality Assessment Service for hCG for a period of 7 years. Among 16 assays used, 4 recognized only hCG, whereas 6 recognized hCG and its free β-subunit (hCGβ), and 6 recognized hCG, hCGβ, and the beta core fragment.

Results: Differences in calibration of current hCG assays are moderate. Mean recovery of the current International Standard (IS), hCG IS 75/589, was 107% (range 93% to 126%), whereas that of the IRR 99/688 for hCG was 139% (range 109%–164%). Between-method variation for the latter (CV 12.3%) was also greater than for IS 75/589 (CV 8.8%). Recognition of hCGβ varied markedly (CV 37%). Most assays overestimated it, but 2 RIAs produced results that were slight underestimations. Recognition of the beta core fragment was even more variable (CV 57%) and was closest to equimolarity for the RIAs.

Conclusions: Assays for hCG show considerable variation in their recognition of various forms of hCG, and this variablility is the most important cause of method-related differences in hCG results in serum and an even more important cause of method-related differences in urine measurements. Equimolar recognition of the major hCG isoforms is essential if between-method comparability for hCG is to be improved.

The following articles in journals at HighWire Press have cited this article:

				A. M. Gronowski and D. G. Grenache Characterization of the hCG Variants Recognized by Different hCG Immunoassays: An Important Step Toward Standardization of hCG Measurements Clin. Chem., August 1, 2009; 55(8): 1447 - 1449. [Full Text] [PDF]