Learning Objective #1: Discuss the difference between clinical and statistical significance in research findings

Learning Objective #2: Discuss the clinical use of the 11-Point Numeric Rating Scale as a pain assessment tool for adults

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Objective: The purpose of this study was to determine the minimum clinically significant difference (MCSD) in patient-assigned, 11-point numeric rating scale (NRS-11) scores for the assessment of pain in adult emergency department (ED) patients. Methods: Rodgers' Science of Unitary Human Beings served as the theoretical framework for this prospective, observational, IRB-approved study. A tertiary care academic ED served as the setting. ED patients presenting with pain were consented and enrolled in this study by an investigator or trained research assistant. Subjects were asked to rate their pain on the NRS-11, a scale of 0 to 10, with 0 being “no pain” and 10 being “the worst pain they could imagine” upon enrollment. Subjects were asked to re-evaluate their pain intensity every 20 minutes for 2 hours. Subjects contrasted this pain with their pain intensity at the previous evaluation. For the contrast, subjects were asked to choose one of the following responses: "a lot more pain," "a little more pain," "about the same pain," "a little less pain," or "a lot less pain." The MCSD was defined as the difference between scores when a subjects' pain was rated "a little more" or "a little less" severe. Results: 354 subjects were enrolled in the study and 1,335 comparisons were made. Of these comparisons, 214 were rated "a little less pain," and 94 were rated "a little more pain." The mean difference between current and preceding NRS-11 scores in these 308 comparisons was 1.39, SD ± 1.05 (95% CI, 1.27-1.51). Conclusions: Findings suggest that the MCSD in patient-assigned NRS-11 pain scores is 1.39, SD ± 1.05 (95% CI, 1.27-1.51).Studies reporting a change of less than 1.39 points may indicate statistical significance, but the findings may not have clinical significance. Additional research is needed to determine the MCSD varies with age, race, or ethnicity.