Human lymphocytes micronucleus assay in Europe. An international survey

The human lymphocytes micronucleus assay has been extensively used in Europe since the cytochalasin-B method was introduced. However, a large range of inter-laboratory variability has been reported, limiting its applicability in European coordinated projects as well as its acceptance in international regulatory guidelines. Thus, an European survey was proposed in order to (a) determine the present state of the human lymphocytes micronuclei assay, (b) review methodological and scientific aspects, and (c) identify discrepancies in the criteria employed by different laboratories that could account for the lack of reproducible results. The outcome of the study with 30 European laboratories surveyed, reflects an immature state of the micronuclei assay in Europe, with (a) disparity in criteria and methodologies, (b) high diversity in the methods of statistical analyses employed, (c) non-uniform criteria for determining positive responses, and (d) a still rare use of new or emerging methodologies. The reported average baseline frequency of micronuclei in human lymphocytes was 7.8 +/- 5.2 per 1000 cells (ranging from 3 to 23), with age and sex but not smoking as being main confounding factors. The general opinion was that more basic research on the micronucleus assay itself is required before considering this technique as an alternative to the chromosomal aberration assay, and that it is a suitable method to detect aneuploidy, mainly in vitro, and specially when coupled with molecular cytogenetic techniques.