ACR Criteria Explained
In clinical trials for rheumatoid arthritis, standard criteria to compare the effectiveness of various arthritis medications or arthritis treatments, or to compare one trial to another trial has become widely used. The criteria, known as ACR Criteria or American College of Rheumatology Criteria, is referred to in nearly all published studies assessing efficacy.
ACR criteria is indicated as ACR20, ACR50, and ACR70. ACR criteria measures improvement in tender or swollen joint counts and improvement in three of the following five parameters:
- acute phase reactant (such as sedimentation rate)
- patient assessment
- physician assessment
- pain scale
- disability/functional questionnaire
What Does ACR20, ACR50, ACR70 Refer to in Clinical Trials?
Clinical trials report the percentage of study participants who achieve ACR20, ACR50, and ACR70. For example, if a study reported that 55 percent of patients achieved ACR20, that means 55 percent of patients in the study achieved a 20 percent improvement in tender or swollen joint counts as well as 20 percent improvement in three of the other five criteria.
If a clinical trial reports that 40 percent of patients achieved ACR50, that means 40 percent of patients in the study achieved a 50 percent improvement in tender or swollen joint counts as well as 50 percent improvement in three of the other five criteria. For patients to be assessed using ACR criteria, they must have completed the trial.
ACR Preliminary Definition of Improvement in Rheumatoid Arthritis. Felson, David T. Arthritis & Rheumatism. June 1995. American College of Rheumatology. 17 Nov 2006.
ACR Definition of Improvement in RA Trials. Johns Hopkins Arthritis. 17 Nov 2006.