Detection of altered pain facilitatory and inhibitory mechanisms in patients with knee osteoarthritis by using a simple bedside tool kit (QuantiPain).

Abstract

Altered pain facilitatory and inhibitory mechanisms have been recognized as an important manifestation in patients with chronic pain, and quantitative sensory testing (QST) can act as a proxy for this process. We have recently developed a simple bedside QST tool kit (QuantiPain) for more clinical use. The purpose of this study was to investigate its test-retest reliability and to evaluate its validity compared with the laboratory-based QST protocols in patients with knee osteoarthritis (OA). QuantiPain consists of 3 items: "pressure algometer" (for pressure pain thresholds [PPTs]), "pinprick" (for temporal summation of pain [TSP]), and "conditioning clamp" (for conditioned pain modulation [CPM]). In experiment-A, intrarater and interrater test-retest reliabilities were investigated in 21 young healthy subjects by using interclass correlation coefficient (ICC). In experiment-B, 40 unilateral painful patients with OA and 40 age-matched, healthy control subjects were included to compare the bedside tool kit against the computerized pressure algometry. In experiment-A, excellent to moderate intrarater and interrater reliabilities were achieved in PPT and TSP (ICC: 0.60-0.92) while the agreements of CPM were good to poor (ICC: 0.37-0.80). In experiment-B, localized and widespread decrease of PPT, facilitated TSP, and impaired CPM was found by using the bedside tool kit in patients with OA compared with controls (P < 0.05). The data were significantly correlated with the established laboratory-based tools (R = 0.281-0.848, P < 0.05). QuantiPain demonstrated acceptable test-retest reliability and assessment validity with the sensitivity to separate patients with painful OA from controls, which has a potential to create more practical approach for quantifying altered pain mechanisms in clinical settings.