Clinical Chemistry
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH
QUICK SEARCH:   [advanced]


     

Clinical Chemistry 0: clinchem.2004.034264v1, 2004; 10.1373/clinchem.2004.034264
This Article
Right arrow Full Text (PDF)
Right arrow Data Supplements
Right arrow All Versions of this Article:
clinchem.2004.034264v1
51/2/401    most recent
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Thaler, M.
Right arrow Articles by Luppa, P. B.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Thaler, M.
Right arrow Articles by Luppa, P. B.

Received on March 18, 2004
Accepted on November 9, 2004

Endocrinology and Metabolism

Immunoassay for Sex Hormone-Binding Globulin in Undiluted Serum Is Influenced by High-Molecular-Mass Aggregates

Markus Thaler 1, Jochen Metzger 1, Anita Schreiegg 1, Barbara Denk 2, Andreas Gleixner 2, Hagen Hauptmann 3, Peter B. Luppa 1*

1 Institute for Clinical Chemistry and Pathobiochemistry, Klinikum rechts der Isar der Techni-schen Universität Mönchen, Munich, German
2 Roche Diagnostics GmbH, Werk Penzberg, Penzberg, Germany
3 Institute of Organic Chemistry, Universität Regensburg, Regensburg, Germany

* To whom correspondence should be addressed. E-mail: luppa{at}klinchem.med.tum.de.

Background: The new Elecsys® chemiluminescence assay for measurement of homodimeric sex hormone-binding globulin (SHBG) was designed for use with undiluted serum, in contrast to other methods that require predilution. During assay development, unexpected calibration difficulties were observed that were attributable to particular biochemical properties of the highly concentrated SHBG in solution.

Methods: We used a surface plasmon resonance (SPR) biosensor, which enables biomolecular interaction analysis of SHBG, and size-exclusion chromatography for this investigation. The immunoassay was evaluated for imprecision, linearity, and suitability of the dilution medium, and the method was compared with an IRMA for SHBG.

Results: The SPR biosensor characterized the special protein properties of SHBG in various concentrations. Above 200 nmol/L there was a strong tendency toward formation of high-molecular-mass aggregates. This was also detectable by size-exclusion chromatography and could be reversed by simple dilution of the sample. On the basis of these results, the dynamic measuring range of the SHBG assay is restricted to 0.350-200 nmol/L. Assay evaluation on a 2010 analyzer revealed excellent precision (CV ≤2.5%). Mean recoveries were 84.2-98.8%. Intermethod comparison with an IRMA yielded a satisfactory concordance of the two assays with a Spearman correlation coefficient of 0.8807.

Conclusions: Aggregates of human SHBG may have a detrimental impact on the accurate measurement of the protein if measurements are performed with undiluted serum samples. Further work is needed to clarify whether these high-molecular-mass aggregates influence the free fraction of steroid hormones in vivo.




HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH
Copyright © 2004 by the American Association for Clinical Chemistry.