American College of Rheumatology criteria for improvement in rheumatoid arthritis should only be calculated from scores that decrease on improvement

Objective. Change in a patient's condition is expressed as a percentage of the baseline value for a core set of measures in the American College of Rh eumatology (ACR) improvement criteria for rheumatoid arthritis (RA), and th is is used as the basis to decide whether a patient has improved. The resul t is dependent on whether the underlying measure has a score that increases or decreases on improvement. We examined the importance of this effect in the application of the ACR improvement criteria. Methods. Data were obtained from the COBRA trial, in which 155 patients wit h early active RA had been randomized to receive either combination treatme nt with step-down prednisolone, methotrexate, and sulfasalazine or sulfasal azine alone. Patient and physician global assessments were recoded to refle ct decreasing scores on improvement. The effects of this difference in scor ing systems were compared among 3 response criteria levels (20%, 50%, and 7 0%) that are currently being used to assess improvement in RA clinical tria ls. Results. Analyses showed that the effects of a decreasing, versus increasin g, score on the designation of improvement cannot be ignored, especially at higher percentages of improvement (e.g., 50%, 70%). Conclusion. We recommend that percentage improvement in RA be calculated on ly on scores that decrease on improvement. When necessary, raw data should be recoded before the ACR improvement criteria are applied.