To evaluate the predictive validity of radiological change on 5-yr disability in rheumatoid arthritis (RA).
The study was designed to be multicentre, prospective, longitudinal, with a 5-yr follow-up. Participants were RA patients (ACR criteria), with a disease duration of <1 yr at entry. Radiographs of the hands and feet in posteroanterior view at baseline and after 12 months of follow-up (van der Heijde's modification of Sharp method) were used for structural evaluation. Disability was evaluated with Health Assessment Questionnaire (HAQ) at yr 5. Analyses consisted of (i) correlation existing between the changes in the radiological scores during the first year and the HAQ value at yr 5 and (ii) determination of the optimal cut-off in the changes in the radiological scoring system, by ROC curve analysis, in which variable to be explained was disability status at yr 5, defined by HAQ value of at least 1.
Due to missing data and/or lost to follow-up, 135 patients (out of the 191 recruited patients) were included in the analyses (mean change in the radiological score = 4.9 +/- 8.7 points, mean HAQ at yr 5 = 0.62 +/- 0.68). There was a statistically significant correlation between the HAQ-disability status at yr 5 and the changes observed in the radiological total damage and narrowing scores during the first year (r = 0.18, P = 0.046 and r = 0.25, P = 0.006, respectively). Conversely, the short-term changes in the erosion score were not correlated with subsequent HAQ-disability (r = 0.084, P = 0.36). A change of at least 2 points in the total X-ray score was considered as optimal (sensitivity, specificity, positive and negative predictive values of 66.7, 53.9, 32.8 and 82.8%, respectively).
This work shows that early changes in joint damage in patients with recent-onset RA are related to subsequent HAQ-disability. This relationship is due to changes in narrowing, rather than in erosion score, suggesting that the joint narrowing score might be of great importance in the follow-up of RA patients and in the reports of scientific results. The weak performance of the thresholds established using predictive validity for subsequent HAQ-disability compromise their use at the individual level.