Relative potency is more than two EC50 values
For a common increasing-response convention, a simple illustrative ratio is reference midpoint divided by test midpoint, multiplied by the assigned reference potency. The orientation and any concentration or preparation corrections must follow the method.
Joint or restricted models can estimate the comparison more directly and use the intended relationship between curves. Either way, sample identity, assigned reference value, dilution factors, model convention, and uncertainty belong with the reported result.
Illustrative ratio: relative potency (%) = EC50(reference) ÷ EC50(test) × 100Test whether the curves support comparison
A potency ratio is interpretable only when the reference and test responses are adequately described over a comparable range. Suitability might address curve shape or parallelism, response range, reference performance, residual behavior, replicate variability, and relative-potency bounds.
There is no universal collection of thresholds. Criteria and handling rules should be justified during method development and validation, then versioned with routine execution.
Build the review package while the analysis runs
Preserve raw wells, plate mapping, concentration calculations, model settings, exclusions with reasons, suitability outcomes, parameters, fitted plots, fingerprints for the source data file and analysis configuration, and the software version.
A report is easier to review when each PASS or FAIL value shows the criterion, observed value, units, outcome, and applicable formatting rule—not just a colored label.
Frequently asked questions
Does relative potency always equal the ratio of EC50 values?
No. That ratio is a useful illustration under compatible curve and concentration conventions. Parallel-line, slope-ratio, jointly fitted nonlinear, or preparation-adjusted methods may define the estimate differently.
What happens when a suitability criterion fails?
The configured outcome should be displayed and reported as a failure. The organization’s procedure determines whether the run is invalidated, investigated, repeated, or otherwise handled; software should not invent that decision.