A novel metric of reliability in pressure pain threshold measurement

Research output: Contribution to journalArticlepeer-review


  • Bernard Liew
  • Ho Yin Lee
  • David Rügamer
  • Alessandro Marco De Nunzio
  • Nicola R Heneghan

External organisations

  • LUNEX International University of Health
  • University of Essex
  • Ludwig-Maximilians-Universität
  • University of Birmingham School


The inter-session Intraclass Correlation Coefficient (ICC) is a commonly investigated and clinically important metric of reliability for pressure pain threshold (PPT) measurement. However, current investigations do not account for inter-repetition variability when calculating inter-session ICC, even though a PPT measurement taken at different sessions must also imply different repetitions. The primary aim was to evaluate and report a novel metric of reliability in PPT measurement: the inter-session-repetition ICC. One rater recorded ten repetitions of PPT measurement over the lumbar region bilaterally at two sessions in twenty healthy adults using a pressure algometer. Variance components were computed using linear mixed-models and used to construct ICCs; most notably inter-session ICC and inter-session-repetition ICC. At 70.1% of the total variance, the source of greatest variability was between subjects (σsubj2 = 222.28 N 2), whereas the source of least variability (1.5% total variance) was between sessions (σsess2 = 4.83 N 2). Derived inter-session and inter-session-repetition ICCs were 0.88 (95%CI: 0.77 to 0.94) and 0.73 (95%CI: 0.53 to 0.84) respectively. Inter-session-repetition ICC provides a more conservative estimate of reliability than inter-session ICC, with the magnitude of difference being clinically meaningful. Quantifying individual sources of variability enables ICC construction to be reflective of individual testing protocols.

Bibliographic note

Publisher Copyright: © 2021, The Author(s).


Original languageEnglish
Article number6944
JournalScientific Reports
Issue number1
Publication statusPublished - 25 Mar 2021