To evaluate replicate effects and test-retest reliability of mechanical and thermal quantitative sensory testing (QST) in normal dogs and dogs with osteoarthritis (OA)-associated pain.
A prospective clinical study.
A total of 54 client owned dogs (OA, n=31; controls, n=23).
Mechanical [electronic von Frey (EVF) and blunt pressure] and thermal (hot and cold) sensory thresholds were obtained in dogs with OA-associated pain and control dogs at two visits, 7 days apart, to assess test-retest reliability. Thresholds were measured at the OA-affected joint (hip or stifle), over the tibial muscle and over the midpoint of the metatarsals. Five replicates were obtained for each modality at each site bilaterally.
Overall, there was no significant effect of replicates on QST response. EVF thresholds were significantly lower at the second visit in OA dogs at the affected and metatarsal sites (p=0.0017 and p=0.0014, respectively). Similarly for control dogs, EVF thresholds were significantly lower at the second visit at the metatarsal site (p=0.001). Significantly higher hot thermal latencies were seen in OA dogs at the affected and tibial testing sites (p=0.014 and p=0.012, respectively), and in control dogs at the tibial site (p=0.004).
If QST is to be used clinically to evaluate a sensitized state, the variability over time needs to be accounted for in the study design.
In QST, a replicate does not show a strong effect. However, QST results show variability over time, particularly for EVF and hot thermal stimuli.