Standardization and validation of dicentric chromosome and gamma h2ax assays for radiation triage and to quantify radiation absorbed dose

Abstract

The H2AX assay was investigated as an alternative to the time consuming dicentric chromosome assay Blood samples collected from healthy volunteers were exposed to varying doses of low LET radiations and constructed dose response calibration cure for DC and H2AX assays For DC assay the scoring was validated within laboratory using centromeric FISH and among various biodosimetry labs in India using inter laboratory comparison exercises Further triage mode scoring was also performed and it showed assay sensitivity of 2 Gy on scoring 20 metaphases Since H2AX foci formation is a kinetic event H2AX assay was performed at 30 and 120 minutes post irradiation The results suggest that the H2AX foci are stable for 120 minutes And H2AX assay by flow cytometry can be a preferred choice because it measures more number of samples in less time does not require trained expertise no scorer variation and importantly the results can be generated in a single day To prove the suitability of H2AX assay for its realistic adoption during radiation triage the blood samples from cancer patients were collected before and after 24 plus or minus 2 hours the first fractionated exposure The estimated dose measured with H2AX assay 92 per cent correlated well with equivalent whole body dose better than DC assay 76 per cent suggesting that H2AX assay can be employed as an alternate triage biodosimetric tool for DC assay during mass causality events to segregate exposed from unexposed and also for precise dose estimation of the exposed individual for the appropriate medical management newline newline newline