Validation of an automatic comet assay analysis system integrating the curve fitting of combined comet intensity profiles

In recent years, the single-cell gel electrophoresis (comet) assay has become a reference technique for the assessment of DNA fragmentation both in vitro and in vivo at the cellular level.In order to improve the throughput of genotoxicity screening, development of fully automated systems is clearly a must. This would allow us to increase processing time and to avoid subjectivity brought about by frequent manual settings required for the ‘classical’ analysis systems.To validate a fully automatic system developed in our laboratory, different experiments were conducted in vitro on murine P388D1 cells with increasing doses of ethyl methanesulfonate (up to 5 mM), thus covering a large range of DNA damage (up to 80% of DNA in the tail). The present study (1) validates our ‘in house’ fully automatic system versus a widely used semi-automatic commercial system for the image-analysis step, and versus the human eye for the image acquisition step, (2) shows that computing tail DNA a posteriori on the basis of a curve fitting concept that combines intensity profiles [G. Dehon, P. Bogaerts, P. Duez, L. Catoire, J. Dubois, Curve fitting of combined comet intensity profiles: a new global concept to quantify DNA damage by the comet assay, Chemom. Intell. Lab. Syst. 73 (2004) 235–243] gives results not significantly different from the ‘classical’ approach but is much more accurate and easy to undertake and (3) demonstrates that, with these increased performances, the number of comets to be scored can be reduced to a minimum of 20 comets per slide without sacrificing statistical reliability.