LAUSR

Biomarkers are commonly used to assess pain and analgesic drug efficacy in livestock. However, the diagnostic sensitivity and specificity of these biomarkers for different pain conditions over time have not been described. Receiver operating characteristic (ROC) curves are graphical plots that illustrate the diagnostic ability of a test as its discrimination threshold is varied. The objective of this analysis was to use area under the curve (AUC) values derived from ROC analysis to assess the predictive value of pain biomarkers at specific timepoints. The biomarkers included in the analysis were blood cortisol, salivary cortisol, hair cortisol, infrared thermography (IRT), mechanical nociceptive threshold (MNT), substance P, and outcomes from a pressure/force measurement system and visual analog scale. A total sample size of 7,992 biomarker outcomes were collected from 6 pain studies involving pain associated with castration, dehorning, lameness, and surgery were included in the analysis. Each study consisted of three treatments; pain, no pain, and analgesia. All statistics were performed using statistical software (JMP Pro 14.0, SAS Institute, Inc., Cary, NC). Results comparing analgesia verses pain yielded good diagnostic accuracy (AUC > 0.7; 95% CI: 0.40 to 0.99) for blood cortisol (timepoints 1.5, 2, and 6 hours); IRT (timepoints 6, 8, 12, and 72 hours); and MNT (timepoints 6, 25, and 49 hours). These results indicate that ROC analysis can be a useful indicator of the predictive value of pain biomarkers and certain timepoints seem to yield good diagnostic accuracy while many do not.