Minimum Significant Ratio (MSR) is a statistical parameter used to measure the variability of results from in vitro dose-response assays. For a given set of assay data, it represents the minimum ratio between two results that is needed to declare those results statistically significantly different from each other (e.g., one compound more potent than another).
A specific usage of MSR is for monitoring production assay results on an ongoing basis. All that is required to do this is that a reference compound be included in each assay run. This will allow calculation of an “overall” MSR, as follows:
where s is the standard deviation of the logged reference results (e.g., IC50).
Incorporation of MSR into production assay monitoring is recommended as a compliment to other quality measures (e.g., Z'-Factor) that typically don't measure between-run variability.
MSR monitoring is now a standard feature of Analyze™ and was introduced at the recent SLAS annual flagship International Conference and Exhibition (San Diego, 2018).
Read more about how Analyze™ uses MSR to measure the variability of results (poster presented at SLAS 2018).