Toxicologic Pathology Forum*: Opinion on the Interpretation of Statistical Significance Testing Results From Anatomic and Clinical Pathology Data in Nonclinical Safety Studies

Toxicologic pathologists assess large data sets from nonclinical studies to identify treatment-related effects to assist in predicting human safety hazards. Statistical testing can facilitate data interpretation by highlighting group differences that have a low probability of random occurrence based on a pre-determined P -value cut-off (eg, P < .05). While this method has been used in the interpretation of pathology data for decades, the appropriateness of utilizing statistical testing in this way has been challenged. Here, we discuss common statistical pitfalls in the analysis of toxicologic pathology data, with emphasis on clinical pathology, reaffirming that appropriate use of statistical analysis requires an understanding of (1) the parameters assessed; (2) the inherent strengths and weaknesses of the statistical method used; and (3) that appropriate interpretation of pathology data is based on the pathologist’s expertise. The presence or absence of statistical significance should not supersede expert judgment but should be one of many tools used to reach a conclusion.