What is the maximum number of levels needed in pain intensity measurement?

TLDR

Pain intensity measurement varies widely, with scales ranging from 4‑point verbal ratings to 101‑point numerical ratings, yet the optimal number of levels remains unresolved. This study aims to provide an empirically derived guideline for selecting the appropriate number of levels in pain intensity scales. We analyzed responses from 124 chronic pain patients who completed 101‑point numerical rating scales for least, most, current, and average pain, then examined how they used the scale and evaluated the sensitivity of seven derived scales ranging from 2 to 101 points. Results show that coding the 101‑point scale as 11‑ or 21‑point scales preserves almost all information, and that 10‑ and 21‑point scales are generally sufficient for chronic pain patients to discriminate pain intensity.

Abstract

An important issue that has yet to be resolved in pain measurement literature concerns the number of levels needed to assess self-reported pain intensity. An examination of treatment outcome literature shows a large variation in the number of levels used, from as few as 4 (e.g., 4-point Verbal Rating scales (VRS)) to as many as 101 (e.g., 101-point Numerical Rating scales (NRS)). The purpose of this study was to provide an empirically derived guideline for determining the number of levels needed. Chronic pain patients (n = 124) provided pre- and post-treatment measures of pain intensity using 101-point NRS for least, most, current, and average pain. The patients' responses to the measures were examined closely to determine the actual number of levels used. In addition, their responses to the 101-point scales were recorded to form 7 scales of varying levels (2- to 101-point scales). The sensitivity of the 7 recorded scales was examined. The results indicated that little information is lost if 101-point scales are coded as 11- or 21-point scales. Moreover, examination of the actual responses to the 101-point measure showed that almost all patients treated it as a 21-point scale by providing responses in multiples of 5 or 10, while a substantial number of patients treated it as an 11-point scale, providing responses in multiples of 10 only. The results suggest that 10- and 21-point scales provide sufficient levels of discrimination, in general, for chronic pain patients to describe pain intensity.