Application of Blood Smears for the Identification of Non-exposed Individuals after a Nuclear Incident.

Healthcare systems will be overwhelmed in the case of a large-scale nuclear incident, not only by members of the exposed population, but also by non-exposed ("worried-well") individuals. Current methods of biodosimetry are time-consuming and resource-intensive for use in a large-scale triage operation. We present a rapid blood smear-based assay utilizing a modified γH2AX assay and a new calculation system (test score) to identify non- or low-exposed individuals within 1 h and 24 h after radiation exposure. Venous blood from seven healthy donors was in vitro irradiated (0-4 Gy) and blood smears were prepared 1 and 24 h postirradiation. Smears were fixed and γH2AX immunostaining was performed. Fifty round nuclei were evaluated by a minimum of seven operators for the presence of γH2AX foci. The proportion of γH2AX foci-positive nuclei, called test score, was used to discriminate between irradiated and non-irradiated samples. Blood smears from non-exposed venous blood were correctly identified as non-exposed within 1 h against a minimum exposure of 0.1 Gy. After 24 h, the smears from non-exposed blood were identified as non-exposed against a minimum exposure of 1 Gy. This result was also validated with blinded samples irradiated at a partner institute. This established protocol was adapted for blood smears generated with capillary blood from three donors, which eliminates the need for a trained professional to draw venous blood and enables the use in field conditions. A discrimination of irradiated and non-irradiated blood was also possible, but thresholds established for venous blood have to be adjusted in future experiments. Together, this fast, operator-friendly assay will allow effective triage in radiological emergencies by reliable exclusion of non-exposed individuals within 6 h of sample arrival, using minimal resources and specialized equipment.