New criteria that define psoriatic arthritis disease activity and treatment response establish cutpoints and percentage changes on the Disease Activity Index for Psoriatic Arthritis scores, Dr. Monika M. Schoels of the Second Department of Internal Medicine at Hietzing Hospital, Vienna, and her coauthors reported.

Dr. Schoels and her colleagues collected 30 patient profiles from an observational data set and then surveyed 44 rheumatology experts (getting 33 responses) to assess the patients’ disease activity based on swollen joint count, tender joint count, global activity, C-reactive protein, and pain ratings. Based on the distribution of Disease Activity Index for Psoriatic Arthritis (DAPSA) scores in the patient population, the investigators then calculated the 25th and 75th percentiles to determine the thresholds for different disease states.

Based on the results, the investigators suggested cutoff values of 4 or less for remission, more than 4 and up to 14 for low disease activity, more than 14 and up to 28 for moderate disease activity, and greater than 28 for high disease activity.

They also found that percentage changes of 50%, 75%, and 85% on the DAPSA corresponded to minor, moderate, and major treatment responses based on American College of Rheumatology 20, 50, and 70 responses observed in three randomized trials.

The study findings provide a “definition of treatment targets … as well as the definition of inclusion criteria for clinical trials for patients in” moderate and high disease activity, Dr. Schoels and her colleagues wrote. “The new response levels will help assess treatment in many settings.”

Read the full study in Annals of the Rheumatic Diseases.