Background Radiological damage is an important outcome measure in rheumatoid arthritis (RA), both for research and clinical purposes. Depending on the setting, both hands and feet are radiographed, or only a part of these. It is unknown whether radiographing part of the four extremities gives comparable information to radiographing both hands and feet. The results of recent MRI studies increased our interest in this issue.
Objectives To compare the radiological information obtained both when evaluating single time-point radiographs and progression over time, in early and advanced RA.
Methods 6,261 sets of hands and feet X-rays of 2,193 RA-patients from Leiden, Groningen (both from Netherlands) and North America were studied. Correlations between joint damage at different regions were compared (unilateral versus bilateral and hands versus feet). Analyses were done at single time-points (cross-sectional) and for progression over time (longitudinal), both for continuous severity measures (Sharp-van der Heijde score, SHS) and binomial measures of erosiveness.
Results When studying single time-points, the severity of joint damage (SHS) is highly correlated between left and right with correlation coefficient more than 0.7, but weakly correlated between hands and feet. Correlation coefficients were higher in advanced than early RA. These findings were comparable in the three datasets. When evaluating erosiveness using only unilateral X-rays or hands without feet, 19.3% and 24.0-40.4% is incorrectly classified as non-erosiveness. Similarly, when evaluating disease progression by imaging only unilateral X-rays or only hands X-rays, progression would have been missed in 11.6-16.2% and 21.2-31.0% of the patients.
Conclusions Evaluations on the presence/absence of erosive disease are preferably done by radiographing both hands and both feet because of the risk of false-negative classification. The severity of joint damage is highly correlated between left and right but not between hands and feet.
Ostergaard M, Dohn UM, Jensen AD et al. Patterns of magnetic resonance imaging bone erosion in rheumatoid arthritis – Which bones are most frequently involved and show the most change? J Rheumatol 2011; 38:2014-2017.
Disclosure of Interest None Declared
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