An in vitro micronucleus assay proficiency study was conducted by member laboratories of the CORESTA In Vitro Toxicity Testing Sub-Group. The purpose of the study was to evaluate the micronucleus induction of a mainstream smoke extract of three cigarettes (Kentucky Reference 1R6F, flue-cured, and burley) using a common study protocol.

This enabled laboratories to evaluate the method proficiency, to compare results with those of other laboratories and to obtain an external audit of documentation procedures that might identify potential areas for improvement. Each laboratory therefore has been able to benefit both technically (scientific methods) and administratively (documentation procedures) from their participation.

The participating laboratories showed excellent performance in delivering replicate results. The median variability of three replicates was about 30 %. The proficiency study showed that the sensitivity of the micronucleus assay is good enough to differentiate the test pieces.