Which performance characteristics does ICH Q2(R2) ask you to validate?

Why

The 2023 revision of Q2 reorganized the old list of characteristics. Specificity or selectivity shows the procedure measures the analyte without interference, which can be proven by absence of interference, by comparison with an orthogonal procedure, or by a justification inherent to the technology. Range replaces the old separate headings for linearity and detection or quantitation limits.

It covers the response, which can be linear, non-linear or multivariate, and validation of the lower range limits. The reportable range is usually derived from the specification. For an assay that is typically 80 to 120 percent of declared content or of the specification limits.

Accuracy is shown against a reference material, by spiking, or by an orthogonal procedure. Precision covers repeatability, with at least 9 determinations across the range or 6 at 100 percent, intermediate precision across days, analysts and equipment, and reproducibility between laboratories when needed. A new option is to assess accuracy and precision together against a combined criterion, using a prediction or tolerance interval.

The purpose decides the set. An identity test needs specificity but not a reportable range, while an impurity test needs a lower range limit. Data from development can count toward validation, so the old habit of repeating everything in a separate study is not required.