Background Synovitis is the key pathological change in rheumatoid arthritis (RA). 2012 updated ACR recommended RA disease activity measures for use in clinical practice included Disease Activity Score with 28-joint counts (DAS28), Clinical Disease Activity Index (CDAI), Simplified Disease Activity Index (SDAI) and Patient Activity Scale (PAS). However, the correlation of these measures with grading of histological synovitis was less reported.
Objectives To explore the correlation of DAS28, CDAI, SDAI, PAS and other clinical indices with grading of histological synovitis in RA.
Methods Synovial tissue was obtained by closed needle biopsy from inflamed knees of 152 consecutive Chinese Han patients with active RA and stained with H&E. The Krenn 3-component synovitis score (lining hyperplasia, inflammatory cell infiltration and stroma activation, each graded on a scale from 0 to 3, yielding a final score from 0 to 9) was performed modified with subscores of two major features of stroma, fibrosis and angiogenesis. According to the Krenn’s synovitis score, patients were divided into no synovitis group(≤1), low-grade synovitis group (1~4) and high-grade synovitis group(>4). Kruskal-Wallis one way analysis of variance on ranks and Spearman’s rank correlation test were used.
Results (1) Among 152 RA patients, 128 (84%) were female, median age was 52 years (range 23~80) and median disease duration was 42 months (range 3~480). The median of Krenn’s synovitis score was 3.5 (range 0.5~6.5). (2) There was significant difference of DAS28-crp and CRP among three groups of different histological synovitis grading (shown in Table 1). DAS28-crp and CRP in high-grade synovitis group were significantly higher than that in no synovitis group (DAS28-crp:χ2=5.973, p=0.015; CRP: χ2=9.313, p=0.002). CRP in low-grade synovitis group was significantly higher than that in no synovitis group (χ2=6.654, p=0.01). (3) Spearman’s rank correlation test showed slight but significant correlation between Krenn’s synovitis score and DAS28-crp (r=0.201, p=0.025), as well as CRP (r=0.225, p=0.005). However, there was no significant correlation between histological synovitis scores and CDAI, SDAI or PAS. (4) High disease activity group of RA patients (DAS28-crp>5.1, n=55) showed significantly higher stroma activation score and fibrosis subscore than in low to moderate disease activity group (DAS28-crp ≥2.6 and ≤5.1, n=97) (stroma activation:χ2=5.419, p=0.02; fibrosis:χ2=5.658, p=0.017). However, histological synovitis scores showed no significant difference among groups of different disease activity according to CDAI, SDAI or PAS.
Conclusions Our results showed DAS28 was better correlated with grading of histological synovitis (especially stroma activation and fibrosis) than other recommended clinical disease activity measures in RA.
Acknowledgements This work was supported by the Chinese National Natural Science Research Grant (grant no. 30972742 and 81001334), the Natural Science Research Grant of Guangdong Province, China (grant no. 9151008901000130 and 10451008901004542) and the Fundamental Research Funds for the Central Universities (no. 10ykpy19).
Disclosure of Interest None Declared