Definition

Measure of disproportionality: (a/(a+b)) / (c/(c+d)) where a=drug+event, b=drug+other, c=other+event, d=other. Thresholds often ≥2 used as screening.

Example

PRR 3.5 for drug X and hepatic failure suggests possible signal.

Regulatory source

Evans et al., GVP Module IX

Common mistakes

Using PRR alone without case count or clinical review.

Inspector question

What PRR threshold do you use and how do you handle small numbers?

Related terms