Laboratory intercomparison on the γ-H2AX foci assay.

Area of Science:

• Radiation biology
• Biophysics
• Medical physics

Background:

• The gamma-H2AX foci assay is a biomarker for DNA double-strand breaks, crucial for assessing radiation exposure.
• Rapid individual dose assessment is vital in radiological incidents for effective medical management.
• Interlaboratory comparisons are essential to evaluate the reliability and reproducibility of biodosimetry techniques.

Purpose of the Study:

• To compare the performance of different laboratories in dose assessment using the gamma-H2AX foci assay.
• To evaluate the gamma-H2AX assay as a triage tool for rapid individual radiation dose assessment.
• To determine the assay's accuracy, sensitivity, and specificity across various dose ranges and repair times.

Main Methods:

• Blood samples were X-irradiated to establish calibration curves (0.25-4 Gy) and tested with blinded samples (0.1-6.4 Gy).
• Samples were incubated for 2 and 24 hours (repair time) before analysis by participating laboratories.
• Dose estimates were compared to actual doses, calculating Mean Absolute Difference (MAD), accuracy, sensitivity, and specificity.

Main Results:

• The gamma-H2AX assay provided dose estimates within 7 hours of sample receipt.
• Accuracy was similar for 2 and 24-hour repair times, indicating utility in early incident phases.
• Despite interlaboratory variability in foci yields, the assay achieved satisfactory accuracy (mean 84%) in discriminating clinically significant dose categories.

Conclusions:

• The gamma-H2AX foci assay is a valuable tool for rapid screening of individuals exposed to radiation, even up to 24 hours post-exposure.
• The assay aids in prioritizing individuals for further cytogenetic dosimetry follow-up.
• Addressing interlaboratory reproducibility issues is crucial for optimizing the assay's widespread application in biodosimetry.