# Frequency and severity response scales for pain and discomfort: psychometric insights from EQ-HWB

## TL;DR

This study compares how well frequency and severity scales measure pain and discomfort, finding that frequency scales provide more information across different health conditions.

## Contribution

The study provides novel psychometric insights into the measurement of pain and discomfort using frequency versus severity scales.

## Key findings

- Frequency scales showed higher informativity than severity scales for both pain and discomfort.
- Severity items had higher discrimination, while frequency items were more sensitive at lower trait levels.
- Immunologic and musculoskeletal conditions were most strongly associated with pain frequency.

## Abstract

Pain and discomfort are core dimensions of health-related quality of life. This study aimed to compare and evaluate the psychometric properties of frequency versus severity response scales in assessing pain and discomfort and determining their unique measurement contributions across different health conditions.

This secondary analysis utilized data from 1,008 participants derived through a dyadic study design of caregivers from the general population and their care recipients. Clinical data were based on self-reported health conditions. Pain and discomfort were assessed using the EQ-5D-5L and EQ-HWB experimental version. The analysis included Spearman's correlation, Shannon's indices, Item Response Theory (IRT), Differential Item Functioning (DIF), and ordinal logistic regression.

Pain frequency and severity items showed a strong correlation (rs=0.81, p<0.001), with similarly strong correlations across all pain and discomfort items (rs>0.5, p<0.001). Frequency scales demonstrated higher informativity than severity scales for both pain (H'=2.28, J'=0.98 vs H'=2.06, J'=0.89) and discomfort (H'=2.18, J'=0.94 vs H'=2.00, J'=0.86). IRT analysis revealed severity items had higher discrimination, while frequency items were more sensitive at lower trait levels. DIF analysis showed significant scale differences for pain (R2=0.24) but not discomfort (R2=0.001). Immunologic (OR=3.21) and musculoskeletal conditions (OR=2.65) were most strongly associated with pain frequency.

Frequency and severity scales capture distinct aspects of pain and discomfort. Frequency scales provide better informativity across trait levels, while severity scales offer superior discrimination at higher intensities. For a comprehensive assessment, both scales are valuable; however, frequency scales may be preferable in shorter instruments due to their broader measurement range and higher informativity.

The online version contains supplementary material available at 10.1007/s11136-025-04003-z.