Long-term effect of TNF inhibitors on radiographic progression in ankylosing spondylitis is associated with time-averaged CRP levels.

OBJECTIVE

To investigate whether the impact of long-term treatment (>3 years) with TNF inhibitors (TNFi) on radiographic progression in AS is associated with the level of acute phase reactants during therapy.

METHODS

One hundred and one consecutive AS patients under TNFi [65 men; age: 41.6±11 years (mean±SD), with symptom duration: 17±10 years] were included in this retrospective study. Lateral X-rays of cervical and lumbar spine, obtained before TNFi initiation, were compared to those obtained after a period of 7±2.5 (range: 3-15) years. The levels of CRP and ESR were evaluated every 6 months. The modified Stoke Ankylosing Spondylitis Spine Score (mSASSS) assessed the radiographic damage. New syndesmophyte formation or ΔmSASSS-score/year≥1 unit/year was defined as radiographic progression.

RESULTS

Forty-seven patients (46.5%) showed radiographic progression. ΔmSASS-score/year was positively correlated with both, baseline CRP (r=0.35, P<0.001) and ESR (r=0.3, P<0.01), as well as with time-averaged CRP (r=0.3, P<0.01). Furthermore, ΔmSASS-score/year was significantly higher (P<0.0001) in patients with syndesmophytes at baseline [0.9 (0.4-1.8), median (IQR)] compared to those without [0 (0-0.4)]. In the multivariate logistic regression analysis, independent risk factors for spinal radiographic progression during TNFi treatment were the presence of syndesmophytes at baseline (OR: 14.7, 95%CI:4.9-44) and the time-averaged CRP>5mg/L (OR:7.6, 95%CI: 2.5-23). No gender differences were observed.

CONCLUSION

In AS patients with long standing disease, radiographic progression during TNFi treatment is significantly associated with higher levels of time-averaged CRP.