A novel metric of reliability in pressure pain threshold measurement

Bernard Liew, Ho Yin Lee, David Rügamer, Alessandro Marco De Nunzio, Nicola R Heneghan, Deborah Falla, David W Evans

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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.

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

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