Absolute Versus Relative Approaches to Severity Scoring of Histopathologic Findings in Pre-Clinical Toxicology Studies: What’s the Difference, and How, When, and Why This Matters

In the field of toxicologic pathology, there are a number of working conventions that are generally understood and practiced by experienced pathologists, despite having received little formal discussion in the published literature. One of these involves the use of an absolute versus relative approach to the semi-quantitative severity scoring of non-neoplastic histopathological findings. Although severity scoring can be performed legitimately using either approach, they have different use-case scenarios, and inherent attributes that may affect the consistency of histopathology data within and among toxicological studies. As a rule, relative scoring is generally more expedient, as it tends to generate fewer diagnoses in both the treated animals and controls, while advantages of the absolute approach include superior objectivity, precision, transparency, and replicability. The purpose of this mini-review is to describe the absolute and relative scoring approaches and discuss potential ramifications that stem from the selection of one approach versus another.