Standardization of two immunoassays for human glandular kallikrein 2

Alexander Haese, Ville Vaisanen, Judith A. Finlay, Kim Pettersson, Harry G. Rittenhouse, Alan Wayne Partin, Debra J. Bruzek, Lori J Sokoll, Hans Lilja, Daniel Wan-Yui Chan

Research output: Contribution to journalArticle

Abstract

Background: Measurement of human kallikrein 2 (hK2) has improved early detection and staging of prostate cancer. However, reported concentrations of hK2 among currently used assays have not been standardized in any way. We compared two hK2 assays and five different recombinant hK2 variants (rhK2) and suggest a common calibrator as an important step and putative reference substance in hK2 assay standardization. Methods: We measured 146 sera by two hK2 assays, using assay-specific calibrators to assess the difference between the two assays. Serial dilutions of five rhK2 preparations were measured repeatedly, with one preparation assigned as calibrator and the others as unknowns to define which variant provided the closest match between the two assays. This rhK2 variant was used to recalibrate both assays. We measured hK2 concentrations in the same 146 patients to evaluate the change in the difference. Results: Use of assay-specific calibrators for comparison of the two assays yielded a Deming regression equation of: y = 0.789 (95% confidence interval, 0.674-0.922)x + 0.014 (0.004-0.025) μg/L; R2 = 0.667. Analysis of five rhK2 variants revealed that the enterokinase (ek)-rhK2 form provided the best match between both assays. Using the ek-rhK2 as a common calibrator, we observed a change in the slope of the regression curve to: y = 1.106 (0.872-1.340)x + 0.006 (-0.002 to 0.016) μg/L; R2 = 0.648, suggesting an increase in the mean estimate of agreement between the two assays. Conclusion: Calibration with a common calibrator substantially increased agreement between the assays. The ek-rhK2 variant provided the best performance of all tested rhK2 variants and should undergo mass spectrometry and amino acid analysis for exact mass determination and value assignment to evaluate its potential as a reference material for immunoassays for hK2.

Original languageEnglish (US)
Pages (from-to)601-610
Number of pages10
JournalClinical Chemistry
Volume49
Issue number4
DOIs
StatePublished - Apr 1 2003

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Tissue Kallikreins
Immunoassay
Standardization
Assays
Enteropeptidase
Calibration
Mass Spectrometry
Prostatic Neoplasms
Confidence Intervals
Amino Acids
Dilution
Mass spectrometry

ASJC Scopus subject areas

  • Clinical Biochemistry

Cite this

Haese, A., Vaisanen, V., Finlay, J. A., Pettersson, K., Rittenhouse, H. G., Partin, A. W., ... Chan, D. W-Y. (2003). Standardization of two immunoassays for human glandular kallikrein 2. Clinical Chemistry, 49(4), 601-610. https://doi.org/10.1373/49.4.601

Standardization of two immunoassays for human glandular kallikrein 2. / Haese, Alexander; Vaisanen, Ville; Finlay, Judith A.; Pettersson, Kim; Rittenhouse, Harry G.; Partin, Alan Wayne; Bruzek, Debra J.; Sokoll, Lori J; Lilja, Hans; Chan, Daniel Wan-Yui.

In: Clinical Chemistry, Vol. 49, No. 4, 01.04.2003, p. 601-610.

Research output: Contribution to journalArticle

Haese, A, Vaisanen, V, Finlay, JA, Pettersson, K, Rittenhouse, HG, Partin, AW, Bruzek, DJ, Sokoll, LJ, Lilja, H & Chan, DW-Y 2003, 'Standardization of two immunoassays for human glandular kallikrein 2', Clinical Chemistry, vol. 49, no. 4, pp. 601-610. https://doi.org/10.1373/49.4.601
Haese A, Vaisanen V, Finlay JA, Pettersson K, Rittenhouse HG, Partin AW et al. Standardization of two immunoassays for human glandular kallikrein 2. Clinical Chemistry. 2003 Apr 1;49(4):601-610. https://doi.org/10.1373/49.4.601
Haese, Alexander ; Vaisanen, Ville ; Finlay, Judith A. ; Pettersson, Kim ; Rittenhouse, Harry G. ; Partin, Alan Wayne ; Bruzek, Debra J. ; Sokoll, Lori J ; Lilja, Hans ; Chan, Daniel Wan-Yui. / Standardization of two immunoassays for human glandular kallikrein 2. In: Clinical Chemistry. 2003 ; Vol. 49, No. 4. pp. 601-610.
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abstract = "Background: Measurement of human kallikrein 2 (hK2) has improved early detection and staging of prostate cancer. However, reported concentrations of hK2 among currently used assays have not been standardized in any way. We compared two hK2 assays and five different recombinant hK2 variants (rhK2) and suggest a common calibrator as an important step and putative reference substance in hK2 assay standardization. Methods: We measured 146 sera by two hK2 assays, using assay-specific calibrators to assess the difference between the two assays. Serial dilutions of five rhK2 preparations were measured repeatedly, with one preparation assigned as calibrator and the others as unknowns to define which variant provided the closest match between the two assays. This rhK2 variant was used to recalibrate both assays. We measured hK2 concentrations in the same 146 patients to evaluate the change in the difference. Results: Use of assay-specific calibrators for comparison of the two assays yielded a Deming regression equation of: y = 0.789 (95{\%} confidence interval, 0.674-0.922)x + 0.014 (0.004-0.025) μg/L; R2 = 0.667. Analysis of five rhK2 variants revealed that the enterokinase (ek)-rhK2 form provided the best match between both assays. Using the ek-rhK2 as a common calibrator, we observed a change in the slope of the regression curve to: y = 1.106 (0.872-1.340)x + 0.006 (-0.002 to 0.016) μg/L; R2 = 0.648, suggesting an increase in the mean estimate of agreement between the two assays. Conclusion: Calibration with a common calibrator substantially increased agreement between the assays. The ek-rhK2 variant provided the best performance of all tested rhK2 variants and should undergo mass spectrometry and amino acid analysis for exact mass determination and value assignment to evaluate its potential as a reference material for immunoassays for hK2.",
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AU - Rittenhouse, Harry G.

AU - Partin, Alan Wayne

AU - Bruzek, Debra J.

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