Original Contributions
Clinically significant changes in pain along the visual analog scale*,**

Presented as an oral presentation at the American College of Emergency Physicians Research Forum, Philadelphia, PA, October 2000.
https://doi.org/10.1067/mem.2001.118012Get rights and content

Abstract

Study Objective: We sought to test the hypothesis that the change in visual analog scale (VAS) associated with a clinically significant change in pain is related to the initial VAS score. Methods: A convenience sample of adults with isolated extremity trauma was enrolled. A VAS score was obtained on entry into the study. Descriptions of change in pain (“lot less,” “little less,” “about the same,” “little more,” or “lot more”) and VAS scores were then obtained every 30 minutes until the patient was free of pain or discharged or a total of 2 hours had passed. Patients were divided into 3 cohorts on the basis of the initial VAS score: VAS score of less than 34, VAS score of 34 to 66, and VAS score of 67 or greater. The absolute values of VAS changes associated with pain descriptions of a “little less” or “little more” (defined as clinically significant), “about the same” (defined as clinically insignificant), and “lot less” or “lot more” were calculated. Results: The change in VAS associated with clinically significant changes in pain in the cohort with VAS scores of less than 34 was 13±14 (mean±SD), which was significantly lower than that of the cohort with VAS scores of 67 or greater (28±21). There was no statistically significant difference in clinically significant changes in pain between the middle cohort and either the upper or lower cohorts (P =.07 and P =.29, respectively). There was no significant change in VAS for clinically insignificant changes in pain among the 3 cohorts (3±4, 6±6, and 8±16, respectively). Conclusion: Patients with greater pain require a greater change in VAS score to achieve clinically significant pain relief. [Bird SB, Dickson EW. Clinically significant changes in pain along the visual analog scale. Ann Emerg Med. December 2001;38:639-643.]

Introduction

Evaluation and management of acute pain is a fundamental element of emergency medical care. Despite the ubiquity of painful conditions, emergency physicians, in general, underestimate1 and undertreat2 their patients' pain. Since the seminal article by Wilson and Pendleton2 demonstrated our collective failure to adequately address patients' pain, a number of authors have investigated methods of more accurately quantifying pain perception,3, 4, 5 as well as areas of physician and nurse biases in treating pain.6, 7, 8, 9, 10, 11 These studies generally use a 100-mm visual analog scale (VAS) to quantify a patient's initial pain, as well as follow the changes in pain over time. Small numeric differences in the VAS score can equate to statistically significant changes in pain; however, these changes are not necessarily of clinical importance.12, 13

Todd et al14 first explored the concept of “minimally clinically significant” change in pain using a VAS. In that investigation, the numeric change on the VAS was linked to the patients' subjective change in pain. The investigators found that a mean difference of 13 mm on a VAS was associated with a patient assessment of either a “little less” or a “little more” pain. Thus, changes in VAS scores of less than 13 mm, although of possible statistical significance, are of questionable clinical significance.

Although Todd et al14 were successful in establishing an initial value associated with a clinically significant change in pain, they failed to determine whether that value was accurate throughout the range of the VAS. What remains to be determined is whether a 13-mm decrease in the VAS from an initial value of 20 mm represents the same change as a 13-mm decrease from a starting value of 90 mm. It is our hypothesis that the absolute change in VAS associated with a minimally clinically significant change in pain is directly related to the initial VAS score.

Section snippets

Materials and methods

This investigation was approved by the University of Massachusetts Medical School Institutional Review Board.

A convenience sample of emergency department patients older than 17 years with isolated extremity trauma was offered enrollment into this prospective study. Exclusion criteria included injury more than 24 hours old or clinically severe intoxication. Demographic data, including age, sex, ethnicity, primary language spoken, time of injury, and time seen in the ED, were documented. For

Results

A total of 77 patients were enrolled in the study. Four patients were excluded from analysis because of incomplete study data. The median time to presentation was 2.4 hours after injury. Demographic data and type of injury are presented in Tables 1 and 2.

. Demographics for all 73 patients.

Patient Demographics%
Men62
Women38
White90.4
Hispanic5.5
Black4.1
English language95.9
Spanish language2.7
Other language1.4

Average patient age was 38.2 y.

. Injury distribution.*

Injury%
Fracture41.9
Sprain or strain41.9

Discussion

In this study, we found that clinically significant changes in pain are not uniform along the entire VAS. Patients with pain in the upper third of the VAS experience a minimally clinically significant change in pain with a greater difference in VAS scores than those patients with pain within the lower third of the VAS. In previous work by Todd et al,14 the mean VAS change in all patients reporting a “little less” or a “little more” pain was 13 mm. However, we found that only in those patients

Acknowledgements

Author contributions: SBB conceived, designed, and supervised data acquisition for this study. SBB drafted the manuscript, and SBB and EWD jointly analyzed the data and contributed to the manuscript revisions. SBB takes overall responsibility for the manuscript.

References (16)

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*

Author contributions are provided at the end of this article.

**

Address for reprints: Steven Bird, MD, Department of Emergency Medicine, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655.

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