Evaluating a sensitive issue: reliability of a clinical evaluation for allodynia severity

Abstract

Purpose/Aim: Allodynia is a common feature of neuropathic pain with few validated clinical evaluation options. We identified a need to estimate the measurement properties of the standardised evaluation procedure for static mechanical allodynia severity popularised by the somatosensory rehabilitation of pain method, known as the rainbow pain scale. This study (www.clinicaltrials.gov. NCT02070367) undertook preliminary investigation of the inter-rater and test-retest reliability of the rainbow pain scale.

Methods: Persons with pain in one upper extremity after Complex Regional Pain Syndrome, a peripheral nerve injury or a recent hand fracture were recruited for assessment of static mechanical allodynia threshold using calibrated monofilaments by two raters at baseline, and repeated assessment one week later.

Results: Single measures estimates suggested inter-rater reliability was substantial for the rainbow pain scale [intra-class correlation coefficient = 0.78 (n = 31), p < 0.001]. Test-retest reliability was also excellent at with an intraclass correlation coefficient of 0.87 [n = 28, p < 0.001]. However, confidence intervals suggest the true values could be more moderate, with lower bounds of the 95% confidence interval at 0.60 and 0.74, respectively.

Conclusions: This pilot study has generated preliminary support for the inter-rater and test-retest reliability of the rainbow pain scale. Future studies should seek to increase confidence in estimates of reliability, and estimate validity and responsiveness to change in persons with somatosensory disorders.

Keywords:

• Neuropathic pain
• allodynia
• reliability
• somatosensory rehabilitation
• Rainbow Pain Scale

Acknowledgements

The authors thank the staff and clients of the Hand Therapy Programme at Hamilton Health Sciences for their support in this endeavour. The authors thank Vicki Fraser, PT; Lisa Galant, OTReg(Ont); and Laura McMicking for their contributions to data collection and management.

Disclosure statement

Claude Spicher serves as the chief executive officer of the Somatosensory Rehabilitation Network. The other authors report no conflict of interest.

Additional information

Funding

This work was supported by the New Investigators Fund [NIF# 13344] at Hamilton Health Sciences. Tara Packham was also supported by a doctoral scholarship from the Canadian Institute of Health Research. Joy MacDermid is supported by a Canadian Institutes of Health Research Chair in Gender, Work, and Health and by the James Roth Chair in Musculoskeletal Measurement and Knowledge Translation. The monofilaments utilised in this study were generously donated by DanMic Global.