Objectives High-resolution peripheral quantitative computed tomography (HR-pQCT) is an emerging imaging technology for early detection of erosion in rheumatoid arthritis (RA). In this study, we use HR-pQCT to investigate the effects of anti-tumor necrosis factor alpha (anti-TNFa) treatment on erosion progression for three months follow-up period.

Methods Fourteen patients with clinically diagnosed RA (Group I, n=4, on methotrexate (MTX) treatment only, and Group II, n=10, on combined anti-TNFa and MTX treatment) underwent clinical evaluation using disease activity score (DAS) score and HR-pQCT scan. Scans were performed on metacarpophalangeal (MCP) joint at baseline (prior to anti-TNF initiation for Group II) in all patients and in twelve patients (4 in group I, 8 in group II) after three months. The maximum width and depth of erosions at the second, third MCP and proximal phalangeal bases (PB) were measured manually in accordance with SPECTRA definition. Erosion volume was calculated as width depth. Mann-Whitney U, Chi-square and paired T-test were done to compare measurements between and within groups from baseline to 3-month.

Results The mean of ages was 71.8±3.8 in group I vs. 49.4±13.6 years in groups II (p=0.019), and of disease duration was 9.0±6.3 vs. 4.0± 4.5 years (p=0.076). The mean of total erosion volume at baseline was 8.0±10.4 mm³ in group I vs. 24.5±42.1 mm³ in group II (p=0.733). In group I, erosions were on PB2 (n=1), MCP2 (n=2), PB3 (n=0), and MCP3 (n=2); in group II, it was 2, 6, 2, and 5 respectively. There was a significant decrease of disease activity in group II (DAS28-CRP, p=0.001 and DAS28–ESR, p=0.002) from baseline to 3-month. Although there was no statistically significance between or within the groups, the mean changes of erosion volume by HR-pQCT tended to increase in group II (0.0±2.5 in group I vs. 4.0±6.8 in group II).

Conclusions At 3 months follow-up, we observed a dissociation between clinical response and erosion volume measured by HR-pQCT in patients on anti-TNFa treatment. The significant decrease in DAS28-CRP, DAS28-ESR and tendency of increase in erosion volumes suggest that although anti-TNFa treatment suppresses inflammation within a 3-month treatment period, the structural joint damage may require more time to be hold. HR-pQCT is a sensitive tool for evaluating erosion volume changes even within a time window of 3-month. Now we are waiting one-year data of our cohort.

Disclosure of Interest None declared