To evaluate at what disease duration and to what extent a ceiling effect, due to reaching maximum scores for erosions (E) and/or joint space narrowing (JSN) in separate joints, started to influence the assessment of radiographic progression according to the modified method of Sharp, in patients with recent onset rheumatoid arthritis (RA).
Prospective followup study of 87 patients with classical or definite RA, joint symptoms <1 year at study entry. Radiographs of hands and feet were made at study entry (Time 0), after 3 (T3), and after 6 years (T6) of followup. Assessment of radiographic progression according to the Van der Heijde modification of Sharp's method. The scores for E and JSN were analyzed separately in the individual groups of joints. Percentages of E joints, of joints with JSN, and of joints with maximum scores were assessed at T0, T3, and T6. The relative risks for the development of radiographic damage and of maximum scores were assessed for the individual joints. An approximation of the magnitude of the ceiling effect was calculated.
After a disease duration of 6 years, a significant influence of a ceiling effect on the mean radiographic progression was found. In some individual patients the ceiling effect appeared to occur earlier. After 6 years, the maximum scores were distributed over 50% of the patients, and 20% of the patients had maximum scores in more than 10 joints without preference for specific localization.
The ceiling effect appeared to be clinically relevant and should be taken into account when interpreting the effects of disease modifying antirheumatic drugs on radiographic progression in RA during the first years of the disease. Furthermore, it must be accounted for when describing the relationship between radiographic progression and process variables.