Micronucleus test for radiation biodosimetry in mass casualty events: Evaluation of visual and automated scoring

In the case of a large-scale nuclear or radiological incidents a reliable estimate of dose is an essential tool for providing timely assessment of radiation exposure and for making life-saving medical decisions. Cytogenetics is considered as the “gold standard” for biodosimetry. The dicentric analysis (DA) represents the most specific cytogenetic bioassay. The micronucleus test (MN) applied in interphase in peripheral lymphocytes is an alternative and simpler approach. A dose-effect calibration curve for the MN frequency in peripheral lymphocytes from 27 adult donors was established after in vitro irradiation at a dose range 0.15–8 Gy of 137Cs gamma rays (dose rate 6 Gy min−1). Dose prediction by visual scoring in a dose-blinded study (0.15–4.0 Gy) revealed a high level of accuracy (R = 0.89). The scoring of MN is time consuming and requires adequate skills and expertise. Automated image analysis is a feasible approach allowing to reduce the time and to increase the accuracy of the dose estimation decreasing the variability due to subjective evaluation.A good correlation (R = 0.705) between visual and automated scoring with visual correction was observed over the dose range 0–2 Gy. Almost perfect discrimination power for exposure to 1–2 Gy, and a satisfactory power for 0.6 Gy were detected. This threshold level can be considered sufficient for identification of sub lethally exposed individuals by automated CBMN assay.