Background Assessment of disease activity is important in the evaluation and monitoring of patients with psoriatic arthritis (PsA) in clinical care and research. As there is no single “gold standard” variable for assessment of disease activity several markers of disease activity are used, among these “global assessment” by the patient (PaGl) and by the physician (PhGl). The agreement and interplay between PaGl and PhGl are not well clarified in patients with PsA, however.
Objectives The objective of the study was to examine associations on the group level and agreements on the individual patient level between PaGl and PhGl as scored on visual analogue scales (VAS) in the daily clinic by patients with active PsA and their rheumatologists.
Methods Traditional disease activity data on 76 PsA patients with active disease planned to initiate biological treatment were extracted from the Danish DANBIO registry. Data comprised swollen joint count (SJC), tender joint count (TJC), CRP, patient and physician global assessment (PaGl and PhGl) and pain (VAS), HAQ-DI and DAS28-CRP (4v). Parametric statistics was used. The predictability of PaGl and PhGl, respectively, by all other disease markers mentioned and by age and sex was examined using stepwise multiple regression analysis. Agreement between the VAS scores was expressed as the bias (mean difference between intra-individual scores) and the 95% lower and upper limits of agreement (LLoA;ULoA) according to the Bland-Altman method.
Results Mean age was 52.2±11.1 years and mean DAS28-CRP 4.7±1.1. 59.2% were of the patients were women. Mean PaGl was 63.7±23.2 and PhGl 39.9±19.8 (p<0.0001). PaGl was significantly but weakly correlated with PhGl (r =0.42, p<0.0001) with a high standard error of estimation (SEE) =21.2. PaGl was independently predicted by pain (beta =0.76, p<0.0001) and HAQ-DI (beta =0.19, p<0.01) and was not predicted by PhGl (p=0.61) (R =0.78, SEE =10.5, p<0.0001). PhGl was independently predicted by SJC (beta =0.43, p<0.0001) followed by pain (beta =0.41, p<0.0001) and CRP (beta =0.20, p<0.05) (R =0.70, SEE =14.4, p<0.0001) with no significantly contribution by PaGl (p=0.49). Differences between the patient-reported VAS-scores were small on the group level but on the individual level they were pronounced: LLoA;ULoA [bias] for PaGl vs. PhGl was -21.9;69.5 [23.8], for PaGl vs. pain -17.1;22.0 [4.9], and for PhGl vs pain -60.8;23.0 [-18.9].
Conclusions In patients with PsA, PaGl was in general scored considerably higher than PhGl. The two scores were poorly connected not only on the individual level but also on group level with no systematic differences between the scores. PaGl was best predicted by pain, and PhGl by SCJ reflecting patients and physicians diverging attitudes to the importance of the different disease manifestations. The findings highlight the challenge of understanding and dealing with discrepancies between assessments and attitudes by physicians and patients.
Disclosure of Interest None declared