Background Patient global assessment (PGA) of disease activity is included in a large number of composite indices of disease activity and definitions of remission in Rheumatoid Arthritis (RA). However, the actual question is formulated in a variety of different ways according to the instrument considered.
Objectives To evaluate how 6 different formulations of PGA affect patient estimates and impact upon disease activity and remission rates as assessed by 4 Disease Activity Indices.
Methods Consecutive RA patients followed in a Rheumatology outpatient department were included in this cross-sectional study. Data collection comprised: 28 joint counts (tender and swollen), C-reactive protein (CRP) and 6 different PGA formulations. The chosen formulations were the ones stated in the: v1) Portuguese National Registry Reuma.pt, the locally used formulation; v2) ACR/EULAR provisional definition of remission (considered in this study as the “standard”); v3) CDAI and SDAI; v4) Disease Activity Score (DAS28) assessment of general health; v5) DAS28 assessment of disease activity (the currently used); v6) one, exploratory, developed by the investigators, including idiomatic cultural expressions. ACR/EULAR Boolean criteria, CDAI, SDAI, and DAS28-CRP (4v) were used to test how these 6 PGA formulations change the rates of remission. PGA differences were assessed by descriptive analyses (including patients with PGA ≤10 and ≤20mm) and Bland-Altman test.
Results In total, 193 patients were included (82% female, mean (SD) age of 59 (13) years, mean disease duration of 12 (9) years and 31% under biologics). The average PGA ranged from 42.3 (25.3) to 48.1 (26.7)mm as measured in different formulations. The ACR/EULAR (v2) formulation yielded the largest proportion of patients scoring ≤10mm (16.1%), corresponding to a difference of up to 4.7% versus other PGAs. Similar results were found for the ≤20 cut-off (Table 1).
By using different PGA's formulations the rates of remission calculated with different indices can vary between 4.7% and 6.7% (Table 2).
Bland-Altman chart confirmed the low agreement between ACR/EULAR formulation and the other PGA formulations (p<.05), except for the DAS “general health” (p=.054).
Conclusions The use of different PGA formulations has clinical implications in disease activity, which, in turn, can influence therapeutic decisions. The establishment of a single standardised formulation seems warranted.
Disclosure of Interest None declared