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 R(2) 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 (R(2) = 0.88; n = 48); and for the
ERSPC group, y = 0.62x - 0.01 (R(2) = 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