Central Pain Mechanisms in Patients With Hand-Osteoarthritis, Psoriatic Arthritis and Healthy Controls

Purpose and rationale for this study: Treating painful hand osteoarthritis (Hand-OA) and psoriatic arthritis (PsA) is a clinical challenge because the exact pain mechanisms remain unknown. Both conditions seem to involve both central and peripheral pain mechanisms and inflammation to some degree. However, it remains unknown whether the pain mechanisms are homogenous among patients with said conditions or if different pain phenotypes exist that may respond differently to treatments. The initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) consortium has recognized this. IMMPACT recommends that clinical trials with chronic pain patients assess different domains of the pain experience (psychosocial, pain qualities, sleep, and pain pathways) to examine if pain phenotypes exist and whether different treatment modalities are more effective for certain phenotypes. Methods: A cross-sectional study examining the difference in pain phenotype and pain mechanisms between patients with Hand-OA, PsA and healthy pain free controls using questionnaire assessments and quantitative sensory testing aiming at investigating pain pathways in the central nervous system. Participants will also have blood drawn to evaluate serological biomarkers for inflammation and joint degeneration. Aim: To examine the pain phenotypes and assess differences in pressure pain threshold between patients with Hand-OA, PsA and healthy pain free controls. Patients and controls: Patients with nodal non-erosive Hand-OA or PsA and visual analogue scale for pain (VAS pain) during the last 24hours of 30mm or more. Controls are healthy age and gender matched subjects with no known chronic pain conditions and maximal pain during last 24 hours under 10mm on a 100mm VAS. Examination programme: All participants will receive a full medical interview and a physical examination which includes auscultation, blood pressure, heart rate and saturation measurements and BMI calculation. All participants will have blood drawn for later examination for markers of inflammation and degeneration. All participants will go through Quantitative Sensory Testing (QST). QST covers a wide range of different examinations techniques used to assess the functional status of the somatosensory system33. In the present study pressure algometry and cuff algometry will be performed. Pain phenotyping: Participants will answer a series of questionnaires related to the pain experience to assess: Anxiety and depression (the hospital anxiety and depression scale), pain catastrophizing (the pain catastrophizing scale), pain description (The short form McGill questionnaire and pain detect questionnaire), sleep quality (Pittsburgh sleep quality index) and a widespread pain assessment questionnaire. To assess function and quality of life the Short form 36 and Health assessment questionnaire will be used. Patients with PsA: Will receive an examination for disease specific tests including: joint tenderness and swelling using the European league against rheumatism (EULAR) 66/68 regiment, dactylitis evaluation using Leeds dactylitis index basic, skin involvement using the psoriasis area and severity index and nail psoriasis via nail psoriasis severity index. Patients with Hand-OA: Will receive the following disease specific examinations evaluation of tender and swollen joints of the hands and wrists. Grip and pinch strength measurements using a hand-held dynamometer.