Validation of a Verbally Administered Numerical Rating Scale of Acute Pain for Use in the Emergency Department

Verbally administered numerical rating scales (NRSs) from 0 to 10 are often used to measure pain, but they have not been validated in the emergency department (ED) setting. The authors wished to assess the comparability of the NRS and visual analog scale (VAS) as measures of acute pain, and to identify the minimum clinically significant difference in pain that could be detected on the NRS.

This was a prospective cohort study of a convenience sample of adults presenting with acute pain to an urban ED. Patients verbally rated pain intensity as an integer from 0 to 10 (0 = no pain, 10 = worst possible pain), and marked a 10-cm horizontal VAS bounded by these descriptors. VAS and NRS data were obtained at presentation, 30 minutes later, and 60 minutes later. At 30 and 60 minutes, patients were asked whether their pain was "much less," "a little less," "about the same," "a little more," or "much more." Differences between consecutive pairs of measurements on the VAS and NRS obtained at 30-minute intervals were calculated for each of the five categories of pain descriptor. The association between VAS and NRS scores was expressed as a correlation coefficient. The VAS scores were regressed on the NRS scores in order to assess the equivalence of the measures. The mean changes associated with descriptors "a little less" or "a little more" were combined to define the minimum clinically significant difference in pain measured on the VAS and NRS.