Validation of the 0–10 verbal numeric scale for assessment of pruritus severity in dogs

BACKGROUND: The pruritus Visual Analog Scale (pVAS) is currently the only validated tool for assessing canine pruritus. A verbal numeric scale (VNS) offers an alternative if clients are not present or able to complete the pVAS.

HYPOTHESIS/OBJECTIVE: To validate the 0-10 VNS and evaluate its interchangeability with the pVAS.

ANIMALS: 251 dogs were included in the study.

MATERIALS AND METHODS: Dog owners were asked to assess their pet's pruritus level using the pVAS, the 0-10 VNS and the verbal rating categories (mild, moderate, severe) in one or two subsequent visits. To be valid, VNS must satisfy the following: correlate with pVAS (criterion validity); indicate reduction in itch score after an antipruritic intervention (construct validity); and have scores related to the verbal rating categories that are significantly different (content validity). VNS and pVAS interchangeability and the percentage of clients that preferred the VNS and pVAS also were evaluated.

RESULTS: The VNS and pVAS correlation for visits 1 and 2 was good (r ICC  = 0.9) and excellent (r ICC  = 0.94). The VNS scores were significantly decreased after antipruritic interventions (P < 0.001). The VNS scores associated with the verbal rating scale categories (mild, moderate and severe) were significantly different (P < 0.001). The 95% limits of agreement for the pVAS and VAS were outside the limit of acceptability of ±2 (-2.0, 2.57). Most clients (69%) preferred the pVAS to the VNS.

CONCLUSIONS AND CLINICAL RELEVANCE: The VNS is a valid scale to evaluate canine pruritus; however, the VNS and pVAS are not interchangeable.