The end of the line? The Visual Analogue Scale and Verbal Numerical Rating Scale as pain assessment tools in the emergency department

Objectives To compare the Visual Analogue Scale ( VAS) and the Verbal Numerical Rating Scale (VNRS), in the assessment of acute pain in the emergency department (ED). Furthermore, to determine the influence of demographics on this agreement and practical limitations of the scales. Setting St Vincent's University Hospital, Dublin; a 479-bed teaching hospital; annual ED census 36 000 adult patients. Methods A prospective observational study was conducted on ED patients with acute pain as a component of their presenting complaint. Eligible patients scored their pain on both VAS and VNRS within 1 hour of arrival. They rescored their pain every 30 minutes for 2 hours using both scales. The primary outcome measure was agreement between VAS and VNRS. Secondary outcomes were ease of pain scale use and effect of patient demographics on pain scores. Agreement between scores was evaluated using the Bland-Altman method. Results 123 patients were included ( median age 35; 43.9% male). There was a strong correlation between VAS and VNRS (r(s)=0.93). However, there was not perfect agreement between the two scales. Patient age (older age, p<0.005, t=-4.448), gender ( female sex, p<0.005, t=4.903) and educational level attained ( third level education, p<0.005, t=5.575) had a statistically significant influence on the agreement between VAS and VNRS. There was a preference for VNRS in those patients who expressed a preference for one pain scale over the other. Conclusions VAS and VNRS are not interchangeable in assessing an individual patient's pain over time in the ED setting. VNRS has practical advantages over VAS in this setting.