RELIABILITY OF QUANTITATIVE SENSORY TESTING, DISEASE ACTIVITY SCORE 28, ULTRASOUND AND CENTRAL ASPECTS OF PAIN QUESTIONNAIRE IN INDIVIDUALS WITH RHEUMATOID ARTHRITIS.

Abstract

Background/Aims Disease Activity Score 28 (DAS28), ultrasound, quantitative sensory testing (QST) and central aspect of pain (CAP) questionnaire measure disease activity and pain hypersensitivity. We investigated their inter-rater and test-retest reliability in Central Aspects of Pain in Rheumatoid Arthritis (CAP-RA) participants. Methods Participants who attended the CAP-RA study visit and agreed to one or more reliability assessments were included. The same two raters completed all assessments, including clinical examination for DAS28, using a single blood sample per participant. QST modalities in the sequence: Pressure Pain detection Threshold (PPT) at the medial joint line of the most painful knee, tibialis anterior and contralateral brachioradialis, Temporal Summation (TS) at rectus femoris of the most painful knee and Conditioned Pain Modulation (CPM), with ischaemic arm pain conditioning and PPT at tibialis anterior. Ultrasound followed the Backhaus 7 protocol, plus the knee. Two trained sonographers scored each joint scan for grey scale (GS), power Doppler and a combined score (PDUS) using EULAR-OMERACT methodology. Joint scores were summated to give an overall score for GS, Doppler and PDUS. Participants could complete questionnaires at invitation, prior to and at baseline, 1-week post-baseline, prior to and at follow-up visit. Any combination of questionnaires completed within 7 days of each other assessed repeatability. Data were assessed for normality, interclass correlation coefficients, and Bland and Altman plots in R studio. Results 196 people were recruited into CAP-RA (median (IQR)) age 66 (58-75) y, 139 (75%) female, 190 (98%) white. 97 (49%) undertook study visits. Characteristics of the 66 people undertaking reliability did not significantly differ from the total population. Measurements are shown in Table 1. Moderate to excellent reliability was found across all measures except CPM (Table 1). The swollen joint count was the least reliable of the DAS28 components. Conclusion Measures of inflammatory disease activity and pain sensitivity are at least moderately reliable within a research context. Only low reliability for CPM might indicate imprecision, or reflect fluctuations in symptoms or pain sensitivity. High reliability of DAS28 and US might reflect relative stability of clinical signs of inflammation. Suppressing day-to-day fluctuations could reduce the unpredictability of rheumatoid arthritis.