DNA and chromosomal damage estimate in blood of people suspected of exposure to radiation

In 1996 four persons were suspected of an accidental exposure to ionizing radiation. In order to estimate the absorbed doses, peripheral lymphocytes were analyzed for the presence of unstable chromosomal aberrations. Additionally, the comet assay was applied for the analysis of DNA damage. Chromosomal aberrations were scored in the first postirradiation metaphase and the absorbed doses reconstructed on the basis of a calibration curve established for lymphocytes irradiated in vitro . All absorbed doses were found to be below 1 Gy. In the comet assay, the absorbed doses were assessed on the basis of dose response relationship and calibration coefficient obtained from the comparison of two DNA damage detection systems. In the case of two persons who received the highest doses, a good agreement was found between chromosomal aberrations and the comet assay. In the case of the other persons, a high level of DNA damage observed in the comet assay did not correlate with a low level of chromosomal aberrations. In the case of one person additional analysis of the sister chromatid exchange (SCE) suggested exposure to chemicals (e.g. long medical treatment or smoking). On the basis of the obtained results we assume that, although the comet assay is sensitive to DNA damage, it is not appropriate for a low radiation dose estimate because, unlike in cytogenetic analysis, one cannot distinguish between DNA damage caused by radiation and other agents. (author)