Background: Pressure pain threshold (PPT) is decreased in several musculoskeletal disorders, giving indirect evidence regarding pain status. Despite the fact that PPT has been already proven to be reliable in patients with acute conditions, there is great variability of methods and results observed within studies, and only a few evidences confirming its reliability in chronic conditions.
Objective: The objective of this study was to determine the test-retest reliability of PPT in the neck and low back regions to discriminate individuals with neck or low back pain from healthy individuals. Additionally, one secondary aim was to establish the minimum detectable change (MDC) and the standard error of measurement for future clinical studies and interventions.
Methods: In this reliability study, 74 individuals (15 individuals from the neck pain and 17 from the neck control group; 21 individuals from the low back pain and 21 from the low back control group). PPT was measured in the neck region (suboccipital, trapezius and supraspinal muscles) and in the lower back region (paraspinal muscles in the levels of L1, L3 and L5). Intrarater reliability was assessed using intraclass correlation coeficient and Bland-Altman.
Results: Excellent intra-rater reliability was observed for both (ICC of 0.874 for the neck pain versus ICC of 0.895 in neck control group; ICC of 0.932 for the low back pain group versus ICC of 0.839 for the control group). A small bias was observed for all groups (-0.08 for the neck pain group versus 0.10 in the control group; and 0.32 in low back pain group versus 0.44 in the control group). Minimum detectable change of 0.63 kgf of neck pain and 1.21 kgf of low back pain was calculated. It was found difference in PPT between pain and control groups (p< 0.05).
Conclusion: It may be suggested that the protocol with PPT is reliable and able to discriminate individuals with and without neck and low back pain with a minor measurement error. Therefore, this method may be used to detect possible progress after interventions in patients with neck or low back pain.
Keywords: Chronic pain; low back pain; neck pain; pain measurement; pressure pain threshold; test reproducibility.