AB0300 Patient Global Assessment, Pain and Fatigue Fluctuate Substantially Over Time in Rheumatoid Arthritis Patients with Stable DAS28-CRP Questioning the Value of These Patient-Reported Markers as Measures of Disease Activity in the Daily Clinic

BackgroundThe interest in the use of patient-reported outcome measures in clinical practice and in clinical trials is increasing. The EULAR/ACR collaborative recommendations 2008 for rheumatoid arthritis (RA) included patient global assessment (PaGl), pain and fatigue (FTG) as key patient-reported outcome measures (ref.). For the clinician, it is essential to know whether an observed change in any disease measure reflects natural variation or “real change”. Natural variation may also be characterized as measurement error. Natural variation is assessed in individuals who are considered to be in “steady state”.ObjectivesTo examine natural variation of PaGl, pain and FTG in patients with stable RA during treatment with biological agents.Methods233 RA patients treated with a biological agent and with stable disease were identified in the Danish rheumatology registry (DANBIO). According to EULAR response criteria, stable disease was defined as a change in DAS28-CRP ≤0.6 between two consecutive visits. Paired data from a single set of such two consecutive visits were extracted for each patient. Data comprised PaGl, pain, FTG and physician global assessment scored on 0-100 VAS scales and DAS28-CRP, tender and swollen joint count, CRP and HAQ-DI. Variation of PaGl, pain and FTG, respectively, was assessed using the Bland-Altman method with calculations of lower and upper 95% limits of agreement (LLoA;ULoA) between two consecutive assessments and the corresponding bias (mean of individual differences). Associations between intra-individual inter-visit differences (Δ) in PaGl, pain and FTG and in other disease activity measures were evaluated by Pearson's linear correlation and stepwise multiple regression analyses.ResultsMean age was 60±15 years, mean inter-visit time duration 22±21 weeks, mean DAS28-CRP 3.1±1.2, mean PaGl 37±27 and mean ΔDAS28-CRP 0.0±0.3 (NS). LLoA;ULoA [bias] was -30;28 [-0.8] for PaGl, -35;36 [0.5] for pain and -36;38 [0.9] for FTG. No significant correlation was found between the absolute Δvalue of PaGl, pain or FTG and the inter-visit time duration (r =0.0 to -0.1, NS). ΔPaGl, ΔPain and ΔFTG were only weakly inter-correlated (r =0.33 to 0.39, p