Psychometric Properties of the Pain Numeric Rating Scale When Applied to Multiple Body Regions among Professional Musicians

Mikhail Saltychev,Ryan Mattie,Martti Vastamäki,Katri Laimi,Heidi Vastamäki,Zachary Mccormick,Pietro Cipresso

doi:10.1371/journal.pone.0161874

Abstract

BackgroundDespite the broad popularity of a numeric rating scale (NRS) its psychometric properties are not well known. The objective was to determine if there is any difference in the discrimination ability of the NRS when used for measuring pain severity separately in different body regions.MethodsCross-sectional survey study of 630 professional musicians. Item Response Theory (IRT) was used to define the psychometric properties of the NRS.ResultsThe discrimination ability of the pain NRS was dependent on the body area to which it was applied. The discrimination was low 0.5 (95% CI 0.4. to 0.7) for the hand region and perfect for the shoulder and upper part of the neck– 3.2 (95% CI 1.2 to 5.2) and 10.5 (95% CI 10.0 to 10.9), respectively. Both shoulder and neck NRSs showed a great shift towards higher levels of pain severity meaning that the ability of the NRS to discriminate low levels of pain is poor. NRS scores obtained from all other regions did not demonstrate any discrimination ability.ConclusionsThe pain NRS might have different psychometric properties depending on the body area to which it is applied. Overall, the modest discrimination ability of the pain NRS implies that it should be used in screening questionnaires with some reservations.

Highlights

The objective was to determine if there is any difference in the discrimination ability of the numeric rating scale (NRS) when used for measuring pain severity separately in different body regions
The discrimination ability of the pain NRS was dependent on the body area to which it was applied
Both shoulder and neck NRSs showed a great shift towards higher levels of pain severity meaning that the ability of the NRS to discriminate low levels of pain is poor

Summary

Introduction

The numeric rating scale (NRS) and visual analogue scale (VAS) are common measurement tools that are found in numerous pain surveys [1]. They have been used in populations with elevated levels of chronic or acute pain, as well as among generally healthy individuals. By using Rasch analysis, Kersten et al and Thomee et al questioned the validity of psychometric abilities of pain VAS [5, 6]. Both of them concluded that the pain VAS does not behave linearly and its responsiveness varies along the trait of pain. The objective was to determine if there is any difference in the discrimination ability of the NRS when used for measuring pain severity separately in different body regions

Objectives

Results

Conclusion