Algometer reliability in measuring pain pressure threshold over normal spinal muscles to allow quantification of anti-nociceptive treatment effects

BackgroundAlgometry has been shown to be an effective way of quantifying pressure pain threshold (PPT), although its reliability in assessing spinal muscle pain (excluding trigger points) has not been robustly analysed.ObjectivesIntra-rater PPT assessment by algometry over the belly of four pairs of spinal muscles (iliocostalis, multifidus, gluteus maximus and trapezius) in a healthy sample was analysed.MethodsHealthy subjects had their PPT measured twice (within 5 min) on three occasions (separated by a week). Intra-class correlation coefficients and the smallest detectable difference were calculated to analyse the reliability of the measurements and 95% limits of agreement plots were drawn to assess systematic difference.ResultsAssessments revealed good within-session reliability (80 assessments) (ICC > 0.91) and good between-session reliability (ICC > 0.87), with a moderate measurement error (approximately 3 kg/cm2) and no systematic difference within-session or between-sessions.ConclusionsPPT assessment by algometry is a reliable, both within-session and between-sessions, measure of a subject's pain. This study provides further validity to the use of this measure as a suitable, convenient method of monitoring treatment effects.