engleski

HUman MicrNucleus Project: International database comparison for results with the cytokinesis-block micronucleus assay in human lymphocytes: I Effects of laboratory protocol, scoring criteria, and host factors on the frequency of micronuclei

Micronucleus(MN) expression in peripheral blood lymphocytes is well established as a standard method for monitoring chromosome damage in human populations. The first results of an analysis of pooled data from laboratories using the cytokinesis-block micronucleus(CBMN) assay and participation in the HUMN (Human Micronucleusproject) international collaborative study are presented. The effects of laboratory protocol, scoring criteria, and host factors on baseline micronucleated binucleated cell (MNC) frequency are evaluated, and a reference range of normal values against which future studies may be compared is provided. Primary data from historical records were submitted by 25 laboratories distributed in 16 countries. This resulted ina database of nearly 7000 subjects. Potentially significant differences were present in the methods used by participating laboratories, such as in the type of culture medium, the concentration of cytochalasin B, the percentage of fetal calf serum and in the culture method. Differences in criteria for scoring micronuclei were also evident. The overall median MNC frequency in nonexposed (i.e. normal) subjects was 6,5% and the interquartile range was between 3 and 12%. An increase in MNC frequency with age was evidente in all but two laboratories. The effect of gender, although not so evident in all databases was also present wtih females having a 19% higher level of MNC frequency (95% confidence interval 14-24%).Statistical analysis were performed using random-effects models for correlated data. Our best model, which included exposure to genotoxic factors, host factors, methods and scoring criteria explained 75% of the total variance, with the largest contribution attributed to laboratory methods.

cytokinesis-block micronucleus assay; peripheral blood lymohocytes; pooled re-analysis; biomarkers; DNA damage

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