HUman MicroNucleus project: international database comparison for results with the cytokinesis‐block micronucleus assay in human lymphocytes: I. Effect of laboratory protocol, scoring criteria, and host factors on the frequency of micronuclei

Abstract

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 participating in the HUMN (HUman MicroNucleus project) international collaborative study are presented. The effects of laboratory protocol, scoring criteria, and host factors on baseline micronucleated binucleate 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 in a 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 per thousand and the interquartile range was between 3 and 12 per thousand. An increase in MNC frequency with age was evident in all but two laboratories. The effect of gender, although not so evident in all databases, was also present, with females having a 19% higher level of MNC frequency (95% confidence interval: 14-24%). Statistical analyses 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 attributable to laboratory methods.

Evaluation of the genetic alterations in direct and indirect exposures of hexavalent chromium [Cr(VI)] in leather tanning industry workers North Arcot District, South India

“…Significant associations were found between age and cytogenetic parameters where age had an influence on the MN frequency of tannery workers. MN frequency has been found to be higher in females (Bonassi et al 2001), while gender differences in comet assay is still a matter of discussion (Heuser et al 2002;Moller 2006). The influence of age in comet assay results are also controversial and still under discussion (Silva et al 2000;Heuser et al 2002Heuser et al , 2007Moller 2006).…”

Genetic damage in humans exposed to extremely low-frequency electromagnetic fields

“…Even the frequencies in the exposed population were much lower than what is normally reported in unexposed control cells. Bonassi et al (2001), for example, reported an overall median micronucleus frequency in non-exposed (i.e. normal) subjects of 6.5 per thousand and an interquartile range between 3 and 12 per thousand.…”

Increased Radiosensitivity as an Indicator of Genes Conferring Breast Cancer Susceptibility

“…This variability together with inconsistent study design is a major reason why the MNT has been almost neglected in the field of breast cancer research despite the fact that almost all published studies revealed significant differences. The test variation is considerable and influenced by type of culture medium, storage time of blood before starting the culture [5], and the persons carrying out visual counting [17]. To overcome these problems, standardization of cell cultures and analysis of confounding factors, as done by the HUMN (HUman MicronNucleus) project [9], have been proposed.…”