Validity of a verbally administered numeric rating scale to measure cancer pain intensity

The ability to quantify pain intensity is essential when caring for individuals in pain in order to monitor patient progress and analgesic effectiveness. Three scales are commonly employed: the simple descriptor scale (SDS), the visual analog scale (VAS), and the numeric (pain intensity) rating scale (NRS). Patients with English as a second language may not be able to complete the SDS without translation, and visually, cognitively, or physically impaired patients may have difficulty using the VAS. The NRS has been found to be a simple and valid alternative in some disease states; however, the validity of this scale administered verbally, without visual cues, to oncology patients has not yet been established. The present study examined validity of a verbally administered 0-10 NRS using convergence methods. The correlation between the VAS and the NRS was strong and statistically significant (r = 0.847, p < 0.001), supporting the validity of the verbally administered NRS. Although all subjects were able to complete the NRS and SDS without apparent difficulty, 11 subjects (20%) were unable to complete the VAS. The mean opioid intake was significantly higher for the group that was unable to complete the VAS (mean 170.8 mg, median 120.0 mg, SD = 135.8) compared to the group that had no difficulty with the scale (mean 65.6 mg, 33.0 mg, SD = 99.7) (Mann-Whitney test, p = 0.0065). The verbally administered 0-10 NRS provides a useful alternative to the VAS, particularly as more contact with patients is established via telephone and patients within the hospital are more acutely ill.