Middlebrook N1,2, Rushton A1,2, Evans DW1,2, Heneghan NR1, Falla D1,2
1University of Birmingham, Centre of Precision Rehabilitation for Spinal Pain (CPR Spine), Birmingham, United Kingdom, 2NIHR Surgical Reconstruction and Microbiology Research Centre (Trauma Research), Birmingham, United Kingdom

Background: It is estimated that 28 million people experience long term pain in the UK, with this number predicted to increase. Quantitative sensory testing (QST), a psychophysical method, allows for quantification of pain and can help predict prognosis in populations including whiplash and osteoarthritis. QST modalities include: pressure and thermal pain thresholds, vibration detection and thresholds, and temporal summation. Current evidence supports use of individual QST components in isolation or in specific populations, but the use of multiple combined modalities is indicated. However, reliability of combined modalities is unknown.

Purpose: To investigate intra and inter-rater reliability of the combined modalities of temporal summation (TS), thermal pain thresholds (TPT) and pressure pain thresholds (PPT).

Methods: A test-re-test study design of within (inter-rater) and between day (intra-rater) was conducted in a University setting with 2 raters and a convenience sample of healthy participants. Four measurements over 2 days, 48 hours apart were completed for each participant. Measurements were taken in the upper limb, lower limb and lumbar spine. Raters, modality, site and laterality were randomised, with temporal summation performed last due to the requirement of PPT scores. Intra-class correlation coefficient (ICC 3,2), 95% confidence intervals (CI), standard error of measurement (SEM) and Bland Altman plots for limits of agreement for between and within day results were calculated. Both raters received training in QST prior to data collection.

Results: 20 participants were recruited (54.4% male, mean (SD) age 27.62 (7.86) years).
TPT: For all sites intra-rater reliability was moderate to excellent (heat ICC range 0.76-0.94, cold ICC range 0.71-0.99) and inter-rater reliability good to excellent (heat ICC range 0.83-0.95, cold ICC range 0.78-0.99). SEM for both raters was 10 for heat and 20 for cold.
PPT: For intra-rater reliability, one lower limb site was rated as poor (ICC 0.41), with the remaining sites ranging from moderate to good (ICC range 0.52-0.88). Inter-rater reliability ranged from moderate to excellent (ICC range 0.66-0.93). SEM varied considerably from 5-9N on day 1, to 3-9N on day 2.
TS: Reliability ranged from poor to excellent for intra rater reliability (ICC range 0.34-0.90) and inter rater reliability (ICC range 0.30-0.92).

Conclusion(s): Results show moderate to excellent reliability for TPT and PPT, however SEM illustrated considerable variability for PPT. The reliability of TS was variable and inconsistent, indicating that participants' pain ratings were changeable within and between sessions. A learning effect of raters and participants, and the possible effect of sensitisation due to number of sites tested could explain the variability in scores and needs to be investigated further.

Implications: QST is a useful tool in research and clinical practice. However, further research and consideration of number of sites tested in a session as well as possible learning effects is warranted. Investigation of the reliability of multiple modalities of QST is now required in symptomatic populations.

Keywords: Quantitative Sensory Testing, Reliability, Pain Mechanisms

Funding acknowledgements: NIHR Surgical Reconstruction and Microbiology Research Centre (Trauma Research)

Topic: Musculoskeletal; Pain & pain management

Ethics approval required: Yes
Institution: University of Birmingham
Ethics committee: University of Birmingham Ethics Committee
Ethics number: ERN_17-0893

All authors, affiliations and abstracts have been published as submitted.

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