Issues related to the experimental design and subsequent statistical analysis of in vivo and in vitro comet studies.

A wide range of experimental designs are used in investigations using the Comet assay. The statistical issues associated with this assay are however not particularly unusual or difficult. It is important however to recognize that the sample rather than the cell is the experimental unit. Statistical analyses based upon measures from the individual cells can lead to serious misinterpretation of results. Interpretation of the results of the assay should be related to identifying changes of biological importance rather than relying solely on the P values of specific statistical tests.