• Reza Ehsanian, Jordan A Buttner, W Evan Rivers, Ameet Nagpal, Jaymin Patel, Patricia Zheng, Zachary McCormick, and Byron J Schneider.
• Division of Pain Medicine, Department of Anesthesia & Critical Care Medicine, University of New Mexico School of Medicine, Albuquerque, NM 87131, United States.
• Pain Med. 2024 Oct 1; 25 (10): 591599591-599.

ObjectiveThe statistical analysis typically used to compare pain before and after interventions assumes that scores are normally distributed. The present study evaluates whether numeric rating scale (NRS) scores, specifically NRS-11 scores, are indeed normally distributed in a clinically relevant cohort of adults with chronic axial spine pain before and after analgesic intervention.MethodsRetrospective review from 4 academic medical centers of prospectively collected data from a uniform pain diary administered to consecutive patients after they had undergone medial branch blocks. The pain diary assessed NRS-11 scores immediately before injection and at 12 different time points after injection up to 48 hours. D'Agostino-Pearson tests were used to test normality at all time points.ResultsOne hundred fifty pain diaries were reviewed, and despite normally distributed pre-injection NRS-11 scores (K2 = 0.655, P = .72), all post-injection NRS-11 data were not normally distributed (K2 = 9.70- 17.62, P = .0001-.008).ConclusionsAlthough the results of parametric analyses of NRS-11 scores are commonly reported in pain research, some properties of the NRS-11 do not satisfy the assumptions required for these analyses. The data demonstrate non-normal distributions in post-intervention NRS-11 scores, thereby violating a key requisite for parametric analysis. We urge pain researchers to consider appropriate statistical analysis and reporting for non-normally distributed NRS-11 scores to ensure accurate interpretation and communication of these data. Practicing pain physicians should similarly recognize that parametric post-intervention pain score statistics might not accurately describe the data and should expect articles to utilize measures of normality to justify the selected statistical methods.© The Author(s) 2024. Published by Oxford University Press on behalf of the American Academy of Pain Medicine. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

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