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


CONCLUSIONS
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.
Wanders
A
A
Department of Internal Medicine, Division of Rheumatology, University Hospital Maastricht, PO Box 5800, 6202 AZ Maastricht, The Netherlands.
Landewé
R
R
Spoorenberg
A
A
de Vlam
K
K
Mielants
H
H
Dougados
M
M
van der Linden
S
S
van der Heijde
D
D
D000328:Adult; D002910:Chronology as Topic; D018450:Disease Progression; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011859:Radiography; D016032:Randomized Controlled Trials as Topic / Q000379:methods*; D015203:Reproducibility of Results; D012107:Research Design; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D013167:Spondylitis, Ankylosing / Q000000981:diagnostic imaging* / Q000188:drug therapy; D013997:Time Factors; D016896:Treatment Outcome