Is a semi-automated approach indicated in the application of the automated micronucleus assay for triage purposes?

Within the EU MULTIBIODOSE project, the automated micronucleus (MN) assay was optimised for population triage in large-scale radiological emergencies. For MN scoring, two approaches were applied using the Metafer4 platform (MetaSystems, Germany): fully automated scoring and semi-automated scoring with visual inspection of the gallery of MN-positive objects. Dose-response curves were established for acute and protracted whole-body and partial-body exposures. A database of background MN yields was set up, allowing determination of the dose detection threshold in both scoring modes. An analysis of the overdispersion of the MN frequency distribution σ(2)/µ obtained by semi-automated scoring showed that the value of this parameter represents a reliability check of the calculated equivalent total body dose in case the accident overexposure is a partial-body exposure. The elaborated methodology was validated in an accident training exercise. Overall, the semi-automated scoring procedure represents important added value to the automated MN assay.