Alkaline comet assay results on fresh and one-year frozen whole blood in small volume without cryo-protection in a group of people with different health status

•To evaluate the impact of small volume blood storage without cryopreservative on the basal level of DNA damage using the comet assay.•Tail intensity values of frozen samples after 1 year at −80 °C were within 11% of allowed values for background controls.•There was significant correlation between TL and TI parameters between fresh and frozen samples in nondiabetic group.•Different health status of individuals can influence on the level of correlation between fresh and frozen samples.•Frozen samples did not have higher percentage of heavily damaged cells and demonstrated that can be used in future studies.