Introduction to Statistics

Abstract

<h3>Background</h3> People with osteoarthritis (OA) can experience both nociceptive pain, as a result of local joint damage, and pain that is indicative of abnormal central pain processing. Quantitative sensory testing (QST) is psychophysical testing of somatosensory function and can been used to investigate somatosensory abnormalities in people with OA. <h3>Objectives</h3> The aim of this study was to assess the reliability discriminant ability of two different mechanical stimuli for QST measurements, pressure and punctate, in people with knee OA and healthy participants. <h3>Methods</h3> Twenty six knee OA participants and 25 healthy participants were recruited. QST was performed in all participants at three sites on the body (sternum, index knee and anterior tibia). Two mechanical QST modalities (pressure and punctate) were performed. Pressure pain threshold (PPT) was assessed using digital algometry. Punctate QST measurements, {mechanical pain threshold (MPT), mechanical pain sensitivity (MPS) and wind-up ratio (WUR)}, were assessed using pinprick stimulators. The procedures were repeated during a second assessment four weeks later by the same examiner to determine repeatability. All participants completed the Intermittent and Constant Osteoarthritis Pain (ICOAP) questionnaire (Rasch transformed). <h3>Results</h3> The mean age for OA participants was 66 years (standard deviation (SD) (9), (50% female) and for the healthy participants was 58 years (SD 11), (48% female). People with knee OA demonstrated significantly higher values on ICOAP Rasch transformed; Intermittent {mean 7.13 (4.47) and Constant mean 4.40 (4.47)} than healthy participants; Intermittent {mean 1.12 (2.31) and Constant {mean 0.29 (1.03)} (<i>P</i>&lt;0.001). The test-retest reliability of the QST measurements before and after 4 weeks interval expressed as intraclass correlation coefficients (ICCs) are given in Table 1. People with knee OA had significantly lower PPT at knee and tibia than normal controls (Graph). Differences between OA and control groups remained significant after adjustment for age and sex. Whereas there were no significant differences found in any punctate QST measurements between knee OA and healthy participants. <h3>Conclusions</h3> This study demonstrated that PPT is a reliable QST measurement with less variability compared to other mechanical QST measurements assessed. PPT at the tibia, a site distal to the affected joint, is believed to reflect augmented central pain processing. PPT may be a preferred QST modality to investigate altered central pain processing in people with OA. <h3>References</h3> R. Rolke et al. Pain 123 (2006), 231 – 243. A.K. Suokas et al. Osteoarthritis Cartilage 10 (2012), 1075–1085 V. Wylde et al. Osteoarthritis Cartilage 19 (2011), 655–658 M Pigg et al. Pain 148 (2010), 220 – 226. <h3>Disclosure of Interest</h3> None declared