Abstract. Objective: Reliable and valid measures of pain are needed to advance research initiatives on appropriate and effective use of analgesia in the emergency department (ED). The reliability of visual analog scale (VAS) scores has not been demonstrated in the acute setting where pain fluctuation might be greater than for chronic pain. The objective of the study was to assess the reliability of the VAS for measurement of acute pain. Methods: This was a prospective convenience sample of adults with acute pain presenting to two EDs. Intraclass correlation coefficients (ICCs) with 95% confidence intervals (95% CIs) and a Bland-Altman analysis were used to assess reliability of paired VAS measurements obtained 1 minute apart every 30 minutes over two hours. Results:The summary ICC for all paired VAS scores was 0.97 [95% CI = 0.96 to 0.98]. The Bland-Altman analysis showed that 50% of the paired measurements were within 2 mm of one another, 90% were within 9 mm, and 95% were within 16 mm. The paired measurements were more reproducible at the extremes of pain intensity than at moderate levels of pain. Conclusions: Reliability of the VAS for acute pain measurement as assessed by the ICC appears to be high. Ninety percent of the pain ratings were reproducible within 9 mm. These data suggest that the VAS is sufficiently reliable to be used to assess acute pain. been done to assess the reliability of the VAS for measurement of acute pain. The few studies that have explicitly assessed the reproducibility of VAS measures of pain focused on chronic or postoperative pain, and most examined the correlation between repeat VAS measures. A study of a mechanical version of a VAS (a tool with a 10-cm ruler and a marker that the patient moves to the point indicating his or her intensity of pain) used by patients with rheumatoid arthritis found a correlation of 0.88 between two measures taken two hours apart. 5 Studies that examined the correlation between a vertically oriented VAS for pain with a horizontally oriented VAS found correlations of 0.99 and 0.91 when they were given within 10 minutes of each other 2,3 to patients with a variety of rheumatic diseases.Although calculation of the Pearson productmoment correlation coefficient has often been used to assess VAS reliability, 2-5 this method has been justly criticized as providing an inflated estimate.9-11 A more appropriate formulation of the correlation coefficient 12 and an analysis of the actual difference between repeated measures have both been recommended. 9 Our primary goal in this study was to assess the reliability of the VAS in acute pain using methodologically appropriate statistical techniques.

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Objectives: 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. Methods: 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 ¼ no pain, 10 ¼ 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. Results: Of 108 patients entered, 103 provided data at 30 minutes and 86 at 60 minutes. NRS scores were strongly correlated to VAS scores at all time periods (r ¼ 0.94, 95% CI ¼ 0.93 to 0.95). The slope of the regression line was 1.01 (95% CI ¼ 0.97 to 1.06) and the y-intercept was À0.34 (95% CI ¼ À0.67 to À0.01). The minimum clinically significant difference in pain was 1.3 (95% CI ¼ 1.0 to 1.5) on the NRS and 1.4 (95% CI ¼ 1.1 to 1.7) on the VAS. Conclusions: The findings suggest that the verbally administered NRS can be substituted for the VAS in acute pain measurement. Key words: pain scales; verbal administration; numerical rating scales. ACADEMIC EMER-GENCY MEDICINE 2003; 10:390-392.A commonly used clinical measure of pain is the numerical rating scale (NRS). Patients are asked to indicate the intensity of pain by reporting a number that best represents it. The NRS is easy to administer verbally in a clinical setting and is a familiar clinical tool. However, there are at least two limitations to its usage in the emergency department (ED): 1) to the best of our knowledge, there have been no studies of its validity in this setting; and 2) a minimum clinically significant difference in pain over time has not been quantified.The visual analog scale (VAS) has been used extensively in clinical research. An advantage of the VAS is that pain is measured continuously. The reliability and validity of the VAS in the ED setting have been demonstrated. [1][2][3][4] The minimum clinically significant difference in pain that can be detected by patie...

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clinicaltrials.gov Identifier: NCT01587274.