Influence of disease-modifying therapy on radiographic outcome in inflammatory polyarthritis at five years: results from a large observational inception study.

OBJECTIVE: To determine the effect of early treatment with disease-modifying antirheumatic drugs (DMARDs) in reducing radiographic progression over a 5-year period in patients with new-onset inflammatory polyarthritis. METHODS: Three hundred thirty-five consecutive patients with paired radiographs obtained 1 year and 5 years after enrollment in a population-based arthritis register were studied. Logistic regression was used to model differences in baseline factors associated with the start of DMARDs. The time from symptom onset to first use of DMARDs was stratified to represent 4 groups: no DMARD use, <6 months, 6-12 months, and >12 months. Radiographs of the hands and feet were scored using the Larsen method. Progression in the Larsen score was evaluated as a 5-year score adjusted for the first film score. Negative binomial regression was used to compare Larsen score progression for each of the 3 treatment groups with that for patients not receiving DMARDs. Results were then adjusted for severity, based on propensity modeling. RESULTS: Patients who received treatment had more radiographic progression than did patients who were untreated. Coefficients (95% confidence intervals), expressed as a multiple of the Larsen score in DMARD-treated patients compared with untreated patients, were as follows: 1.6 (1.1-2.3) for <6 months, 2.4 (1.5-3.6) for 6-12 months, and 2.0 (1.4-2.8) for >12 months. As expected, patients receiving treatment had more severe disease at baseline. Using the propensity score as a method of adjusting for disease severity, the influence of treatment on outcome became attenuated as follows: 1.1 (0.8-1.7) for <6 months, 1.6 (1.0-2.6) for 6-12 months, and 1.5 (1.0-2.2) for >12 months. This effect was also seen in the crude Larsen score at year 5. CONCLUSION: In this observational study, DMARD treatment was a marker not only of worse disease at presentation but also of the radiographic state and radiographic progression at 5 years. After adjustments were made for baseline disease severity, earlier therapy was shown to have a beneficial effect on outcome.