EXTENDED REPORT

Scoring of radiographic progression in randomised clinical trials in ankylosing spondylitis: a preference for paired reading order

A Wanders¹, R Landewé¹, A Spoorenberg¹, K de Vlam², H Mielants², M Dougados³, S van der Linden¹, D van der Heijde¹

¹ Department of Internal Medicine, Division of Rheumatology, University Hospital Maastricht, The Netherlands
² Department of Rheumatology, University Hospital Gent, Belgium
³ Department of Rheumatology, Hôpital Cochin Paris, France

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

Objectives: To describe the influence of the reading order (chronological v paired) on radiographic scoring results in ankylosing spondylitis. To investigate whether this method is sufficiently sensitive to change because paired reading is requested for establishing drug efficacy in clinical trials.

Methods: Films obtained from 166 patients (at baseline, 1 year, and 2 years) were scored by one observer, using the modified Stoke Ankylosing Spondylitis Spinal Score. Films were first scored chronologically, and were scored paired 6 months later.

Results: Chronological reading showed significantly more progression than paired reading both at 1 year (mean (SD) progression 1.3 (2.6) v 0.5 (2.4) units) and at 2 years (2.1 (3.9) v 1.0 (2.9) units); between-method difference: p<0.001 at 1 year, and p<0.001 at 2 years. After 1 year, progression (>0 units) was found in 35/166 (21%) patients after paired reading and in 55/166 (33%) after chronological reading. After 2 years, these figures were 50/166 (30%) and 68/166 (41%), respectively. Sample size calculations showed that 94 patients in each treatment arm are required in a randomised clinical trial (RCT) to provide sufficient statistical power to detect a difference in 2 year progression if films are scored paired.

Conclusion: Reading with chronological time order is more sensitive to change than reading with paired time order, but paired reading is sufficiently sensitive to pick up change with a follow up of 2 years, resulting in an acceptable sample size for RCTs.

Abbreviations: AS, ankylosing spondylitis; D-CART, disease controlling antirheumatic treatment; RA, rheumatoid arthritis; RCT, randomised controlled trial; SASSS, Stoke Ankylosing Spondylitis Spinal Score

Keywords: radiographs; radiographic progression; reading order; ankylosing spondylitis; randomised controlled trials

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• BARALIAKOS, X., LISTING, J., von der RECKE, A., BRAUN, J. (2009). The Natural Course of Radiographic Progression in Ankylosing Spondylitis -- Evidence for Major Individual Variations in a Large Proportion of Patients. The Journal of Rheumatology 36: 997-1002 [Abstract] [Full Text]  
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