Background Impaired function and spinal mobility in patients with ankylosing spondylitis (AS) can be caused by both spinal inflammation and new bone formation. Anti-TNF therapy has been shown to reduce inflammation but the influence on radiographic progression is less clear.
Objectives To investigate the impact of long-term (up to 10 years) anti-TNF therapy on function and spinal mobility in relation to radiographic progression in the spine in patients with AS.
Methods Altogether 60 patients with AS from two long-term trials with TNF blockers (43 on infliximab  and 17 on etanercept ) were included in this completer analysis based on availability of spinal x-rays performed at baseline and at least at one following time-point (year 2, 4, 6, 8, 10) during the follow-up. Spinal radiographs (cervical and lumbar spine lateral views) were scored according to the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS) system by two readers (DP and AF) not blinded for the time point. The functional status was assessed by means of the Bath Ankylosing Spondylitis Functional Index (BASFI), spinal mobility – by the Bath Ankylosing Spondylitis Metrology Index (BASMI, 0-10), and clinical disease activity - by the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI).
Results Patients treated with infliximab and etanercept had similar baseline characteristics with regards of age, gender, HLA-B27 status, symptom duration, disease activity and baseline structural damage that allowed pooling of the data. There was a good agreement between readers regarding the mSASSS with an intra-class correlation coefficients of >0.9 at all time-points. The dynamics of the mSASSS score, BASDAI, BASFI and BASMI over 10 years at the group level (data as observed) are presented in the figure. After the BASFI had initially improved significantly in response to anti-TNF therapy in those patients who remained on the drug over time it remained remarkably stable at low levels over 10 years despite the observed increase of the mSASSS by 6 points in the same patients. Similarly, BASMI had improved significantly after initiation of anti-TNF therapy and remained at the low level until year 10: baseline – 3.5, year 2 – 2.5, year 4 – 2.1, year 6 – 2.1, year 8 – 2.5, year 10 – 2.7. The BASDAI also remained stable at levels <3 indicating good control of disease activity.
Conclusions Functional status in patients with advanced AS remained stable during long-term anti-TNF therapy despite some radiographic progression. Under these conditions the BASFI course correlated strongly with BASDAI but not with the mSASSS. This might indicate that a good control of inflammation is able to overweight the negative effect of structural damage in the spine on the functional status in AS.
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Disclosure of Interest D. Poddubnyy Consultant for: AbbVie, MSD, Pfizer, UCB, Speakers bureau: AbbVie, MSD, Pfizer, UCB, A. Fedorova: None declared, J. Listing: None declared, H. Dyck: None declared, H. Haibel Consultant for: Abbvie, MSD, Speakers bureau: Abbvie, X. Baraliakos Consultant for: AbbVie, MSD, Pfizer, UCB, Speakers bureau: AbbVie, MSD, Pfizer, UCB, J. Braun Grant/research support from: Abbvie, MSD, Pfizer, Consultant for: AbbVie, MSD, Pfizer, UCB, Speakers bureau: AbbVie, MSD, Pfizer, UCB, J. Sieper Grant/research support from: Abbvie, MSD, Pfizer, Consultant for: AbbVie, MSD, Pfizer, UCB, Speakers bureau: AbbVie, MSD, Pfizer, UCB