Initial Content Validation and Roadmap for a New Patient-Reported Outcome Measure of Pain Intensity

The level of agreement between the numerical rating scale and visual analogue scale for assessing pain intensity in adults with chronic pain

The numerical rating scale and visual analogue scale are used to quantify pain intensity. However, it has not yet been explored whether these scores are interchangeable in adults with chronic pain. Data from the prospective multicentre cross-sectional INTERVAL study were used to evaluate the one-dimensionality and agreement between numerical rating scale scores and visual analogue scale scores in adults with chronic pain. Pain intensity scores using the numerical rating scale and visual analogue scale were provided by 366 patients with chronic pain for current, average, minimal and maximal pain. To evaluate whether pain intensity scales are completed in accordance with each other, the proportion of patients who satisfied the following condition was calculated: minimal pain intensity ≤ maximal pain intensity. A factor analysis confirmed the one-dimensionality of the pain measures. A significant difference was found between numerical rating scale and visual analogue scale scores for average, current, minimum and maximum pain. Intra-class correlation coefficient estimates ranged from 0.739 to 0.858 and all measures failed to show sufficient and acceptable agreement at the 95% level. The strength of agreement between pain severity categories was classified as 'moderate' for average and minimal pain and 'substantial' for current and maximal pain. The proportion of patients who scored minimal pain ≤ maximal pain was 97.5% for the numerical rating scale and 89.5% for the visual analogue scale. This study failed to show an acceptable agreement between the numerical rating scale and visual analogue scale when pain intensity was rated by adults with chronic pain, despite showing both scales measure the same information.

The Sensation and Pain Rating Scale: easy to use, clear to interpret, and responsive to clinical change

Background

The Sensation and Pain Rating Scale (SPARS) allows rating of non-painful as well as painful percepts. While it performs well in the experimental context, its clinical utility is untested. This prospective, repeated-measures study mixed qualitative and quantitative methods to examine the utility and performance of the SPARS in a clinical context, and to compare it with the widely used 11-point NRS for pain.

Methods

People presenting for outpatient physiotherapy (n = 121) provided ratings on the SPARS and NRS at first consultation, before and after sham and active clinical interventions, and at follow-up consultation. Clinicians (n = 9) reported each scale's usability and interpretability using Likert-type scales and free text, and answered additional questions with free text. Each data type was initially analysed separately: quantitative data were visualised and the ES II metric was used to estimate SPARS internal responsiveness; qualitative data were analysed with a reflexive inductive thematic approach. Data types were then integrated for triangulation and complementarity.

Results

The SPARS was well received and considered easy to use, after initial familiarisation. Clinicians favoured the SPARS over the NRS for clarity of interpretation and inter-rater reliability. SPARS sensitivity to change was good (ESII=0.9; 95%CI: 0.75-1.10). The greater perceptual range of the SPARS was deemed especially relevant in the later phases of recovery, when pain may recede into discomfort that still warrants clinical attention.

Conclusion

The SPARS is a promising tool for assessing patient percept, with strong endorsement from clinicians for its clarity and superior perceptual scope.

Expectations for Improvement: A Neglected but Potentially Important Covariate or Moderator for Chronic Pain Clinical Trials

Variability in pain-related outcomes can hamper assay sensitivity of chronic pain clinical trials. Expectations of outcome in such trials may account for some of this variability, and thereby impede development of novel pain treatments. Measurement of participants' expectations prior to initiating study treatment (active or placebo) is infrequent, variable, and often unvalidated. Efforts to optimize and standardize measurement, analysis, and management of expectations are needed. In this Focus Article, we provide an overview of research findings on the relationship between baseline expectations and pain-related outcomes in clinical trials of pharmacological and nonpharmacological pain treatments. We highlight the potential benefit of adjusting for participants' expectations in clinical trial analyses and draw on findings from patient interviews to discuss critical issues related to measurement of expectations. We conclude with suggestions regarding future studies focused on better understanding the utility of incorporating these measures into clinical trial analyses. PERSPECTIVE: This focus article provides an overview of the relationship between participants' baseline expectations and pain-related outcomes in the setting of clinical trials of chronic pain treatments. Systematic research focused on the measurement of expectations and the impact of adjusting for expectations in clinical trial analyses may improve assay sensitivity.