Comparison of results of the manual and automated scoring of micronucleus frequencies in (60)Co-irradiated peripheral blood lymphocytes for triage dosimetry.

Scoring micronuclei in the peripheral blood lymphocytes of individuals exposed to ionizing radiation is a rapid biodosimetry assay. Peripheral blood lymphocytes from five individuals were exposed in vitro to 0-5Gy of (60)Co γ-radiation at a dose rate of 0.76Gy/min. The blood cultures were initiated with RPMI-1640 (80%) supplemented with FBS (20%), stimulated with mitogen and incubated at 37°C for 44h. At the 44th hour, cytochalasin-B (6µg/mL) was added, and the cultures were incubated for 28h more. The cells were harvested with a pre-chilled hypotonic solution (0.075M) and fixed with a Carnoy's solution (methanol/acetic acid 5:1). Giemsa- and propidium-iodide-stained cells affixed to slides for microscopy were scored manually and automatically with the micronucleus scoring software from MetaSystems. The micronucleus frequencies determined in the Giemsa-stained cells by manual and automated scoring were 23.6% different (P<0.0001) with an efficiency of 24.9%. Slides stained with propidium iodide are a better choice for automated scoring than Giemsa-stained ones.