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Comparison of Two Assays for Human Kallikrein 2

Departments of
¹ Clinical Chemistry and
² Urology, University Hospital Rotterdam, 3000 CA Rotterdam, The Netherlands.
³ Department of Molecular Diagnostics, Hybritech Inc., a subsidiary of Beckman Coulter Inc., San Diego, CA 92196-9006.

⁴ Department of Biotechnology, University of Turku, 20520 Turku, Finland.

^aAddress correspondence to this author at: Department of Clinical Chemistry, University Hospital Rotterdam, PO Box 2040, 3000 CA Rotterdam, The Netherlands. Fax 31-10-4367894; e-mail blijenberg{at}ckcl.azr.nl.

Background: We compared two recently developed research assays for the measurement of human kallikrein 2 (hK2) in serum: one fully automated assay (Beckman Coulter Access® immunoanalyzer) and one manual assay based on the DELFIA® technology.

Methods: We used two subsets of clinical specimens consisting of 48 samples from prostate cancer patients and 210 samples from participants in an ongoing screening study (ERSPC). Both subsets were measured in the Rotterdam laboratory, and the prostate cancer samples were used for analytical comparison with the originating sites for the assays: Beckman Coulter Research Department (San Diego, CA) and Turku University (Turku, Finland).

Results: Both the Beckman Coulter and the Turku assays performed very similarly between the Rotterdam laboratory and the originating sites: the R² value for both comparisons was 0.99, and the slope difference between sites was <20%. Deming regression analysis of the DELFIA (y) and Access (x) assays yielded the following: for the prostate cancer group, y = 1.17x - 0.01 (R² = 0.88; n = 48); and for the ERSPC group, y = 0.62x - 0.01 (R² = 0.77). Breakdown of the latter group into subgroups (nondiseased, benign prostatic hyperplasia, and prostate cancer samples) gave only minor differences. The Access calibrators were underrecovered by 13% in the DELFIA assay, whereas the DELFIA calibrators were overrecovered by 45% in the Access assay.

Conclusion: The DELFIA and Access assays for hK2, which have similar analytical features, show differences that cannot be explained by calibration.

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

				V. Vaisanen, S. Eriksson, K. K. Ivaska, H. Lilja, M. Nurmi, and K. Pettersson Development of Sensitive Immunoassays for Free and Total Human Glandular Kallikrein 2 Clin. Chem., September 1, 2004; 50(9): 1607 - 1617. [Abstract] [Full Text] [PDF]