Background Joint counts performed by the rheumatologist, included in indices such as DAS (Disease Activity Score), are the main measure of disease activity in patients with Rheumatoid Arthritis (RA) and Psoriatic Arthritis (PsA) with peripheral joint disease. Nevertheless, self-reported outcomes are also used to assess disease activity and treatment response. In a previous analysis of the Arthro-perception study, authors found moderate to strong correlation between patient self-reported and physician's joint counts in PsA and only weak to moderate correlation in RA. However, are there other factors influencing this level of agreement?
Objectives To identify predictors of concordance between patient and physician's assessment in RA and PsA.
Methods A convenient sample of outpatients with RA and PsA attending a Rheumatology clinic was recruited. The participants were asked to fill out a questionnaire while they were in the waiting area. This included a disease activity visual analog scale (VAS) and three homunculi, in which the patients were asked to point tender, swollen and deformed joints out of 44 possible locations. After this, participants were examined by rheumatologists who also recorded their evaluation in a similar questionnaire. Statistical analysis was performed using IBM® SPSS® Statistics version 20. Spearman correlation coefficient (rs) was used to examine the correlation between patient and physician's joint counts in several subgroups based on gender, education, duration of disease, patient's VAS and DAS28(3). Statistical significance was set at 0.05.
Results 114 patients were included, 68 with RA (75% females) and 46 with PsA (70% males). PsA patients' self-reported joint counts had moderate to strong correlation with physician's assessment in men [rs =0.68 (tender and swollen), 0.44 (deformed)]; whereas there was no significant correlation in women. In RA group the correlation for tender joint counts was also better in men (rs =0.48 vs 0.35); the opposite was found for swollen and deformed joints, where there was moderate correlation in women (rs =0.40 and 0.43, respectively) and no significant correlation in men. In PsA group, there was moderate to strong correlation between patient and physician's assessment in patients with low activity disease - DAS 28(3) <3.2 [rs =0.51 (tender), 0.39 (swollen) and 0.68 (deformed)]; whereas there was no significant correlation in patients with DAS 28(3) >3.2. The same was found in RA patients but only for tender joints (rs =0.40), whereas for swollen and deformed joints there was correlation only in patients with DAS 28(3) >3.2 [rs =0.48 (swollen) and 0.55 (deformed)]. PsA patients' VAS inferior to 50mm was associated with moderate to strong correlation [rs =0.73 (tender), 0.60 (swollen), 0.58 (deformed)], which was not significant for higher values of VAS. Oppositely, in RA group, correlation for tender and deformed joints was better when VAS is higher (rs =0.42 and 0.37). Duration of disease inferior to 4 years and less than 9 years of education were associated with a stronger correlation in both groups.
Conclusions Male gender and low disease activity may be predictors of agreement between patient and physician's assessment in PsA. Short disease duration and low education also appear, paradoxically, to predict a better agreement, both in RA and PsA.
Disclosure of Interest None declared