EXTENDED REPORT

Association between radiographic damage of the spine and spinal mobility for individual patients with ankylosing spondylitis: can assessment of spinal mobility be a proxy for radiographic evaluation?

A Wanders¹, R Landewé¹, M Dougados², H Mielants³, Sj van der Linden¹, D van der Heijde¹

¹ University Hospital Maastricht, Maastricht, The Netherlands
² Hôpital Cochin, Paris, France
³ University Hospital Ghent, Ghent, Belgium

Correspondence to:
Correspondence to:
Dr R Landewé
University Hospital Maastricht, Department of Internal Medicine, Division of Rheumatology, PO Box 5800, 6202 AZ Maastricht, The Netherlands; rlan{at}sint.azm.nl

Objective: To demonstrate the association between various measures of spinal mobility and radiographic damage of the spine in individual patients with ankylosing spondylitis, and to determine whether the assessment of spinal mobility can be a proxy for the assessment of radiographic damage.

Methods: Radiographic damage was assessed by the mSASSS. Cumulative probability plots combined the radiographic damage score of an individual patient with the corresponding score for nine spinal mobility measures. Receiver operating characteristic analysis was performed to determine the cut off level of every spinal mobility measure that discriminates best between the presence and absence of radiographic damage. Three arbitrary cut off levels for radiographic damage were investigated. Likelihood ratios were calculated to explore further the diagnostic properties of the spinal mobility measures.

Results: Cumulative probability plots showed an association between spinal mobility measures and radiographic damage for the individual patient. Irrespective of the chosen cut off level for radiographic progression, lateral spinal flexion and BASMI discriminated best between patients with and those without structural damage. Even the best discriminatory spinal mobility assessments misclassified a considerable proportion of patients (up to 20%). Intermalleolar distance performed worst (up to 30% misclassifications). Lateral spinal flexion best predicted the absence of radiographic damage, and a modified Schober test best predicted the presence of radiographic damage.

Conclusion: This study unequivocally demonstrated a relationship between spinal mobility and radiographic damage. However, spinal mobility cannot be used as a proxy for radiographic evaluation in an individual patient.

Abbreviations: AS, ankylosing spondylitis; AUC, area under the curve; BASMI, Bath Ankylosing Spondylitis Metrology Index; BASRI, Bath Ankylosing Radiography Index; LR, likelihood ratio; MRI, magnetic resonance imaging; mSASSS, modified Stoke Ankylosing Spondylitis Spinal Score; NPV, negative predictive value; PPV, positive predictive value; ROC, receiver operating characteristic

Keywords: radiographic damage; spinal mobility; ankylosing spondylitis

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

• BOONEN, A., CRUYSSEN, B. v., de VLAM, K., STEINFELD, S., RIBBENS, C., LENAERTS, J., Van den BOSCH, F., MIELANTS, H., DEWULF, L., VASTESAEGER, N. (2009). Spinal Radiographic Changes in Ankylosing Spondylitis: Association with Clinical Characteristics and Functional Outcome. The Journal of Rheumatology 36: 1249-1255 [Abstract] [Full Text]  
• Landewe, R, Dougados, M, Mielants, H, van der Tempel, H, van der Heijde, D (2009). Physical function in ankylosing spondylitis is independently determined by both disease activity and radiographic damage of the spine. Ann Rheum Dis 68: 863-867 [Abstract] [Full Text]  
• Braun, J., Sieper, J. (2008). What is the most important outcome parameter in ankylosing spondylitis?. Rheumatology (Oxford) 47: 1738-1740 [Full Text]  
• van der Heijde, D, Landewe, R, Feldtkeller, E (2008). Proposal of a linear definition of the Bath Ankylosing Spondylitis Metrology Index (BASMI) and comparison with the 2-step and 10-step definitions. Ann Rheum Dis 67: 489-493 [Abstract] [Full Text]  
• Braun, J, Baraliakos, X, Listing, J, Fritz, C, Alten, R, Burmester, G, Krause, A, Schewe, S, Schneider, M, Sorensen, H, Zeidler, H, Sieper, J (2008). Persistent clinical efficacy and safety of anti-tumour necrosis factor {alpha} therapy with infliximab in patients with ankylosing spondylitis over 5 years: evidence for different types of response. Ann Rheum Dis 67: 340-345 [Abstract] [Full Text]