Measuring cell proliferation in the rectal mucosa: comparing bromodeoxyuridine (BrdU) and proliferating cell nuclear antigen (PCNA) assays

Cell proliferation in the human colorectum can be measured using bromodeoxy uridine (BrdU) or proliferating cell nuclear antigen (PCNA) assays. Using d ata from the National Cancer Institute's Polyp Prevention Trial, these two assays are compared using correlation coefficients and variance components analysis. Adjusting for fixed as well as for the random effects of between- biopsy and scoring variation, the estimated correlation is 0.46 for the log labeling index and 0.45 for log proliferative height. This is an estimate of the highest correlation that can be achieved by taking multiple biopsies scored by multiple scorers. For single biopsies, the estimated correlation is 0.16 and 0.10, respectively. There are significant differences between the variance components for the two assays. For example, for log labeling i ndex, PCNA has a lower variation between biopsies than BrdU, but higher var iation between scorings, When used in a clinical or epidemiological setting , it is important to take multiple biopsies at multiple time points. (C) 20 00 Elsevier Science Inc. All rights reserved.