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• There is no single laboratory test or procedure that can be used to diagnose RA; instead a set of criteria that includes clinical symptoms (stiffness, swelling), radiographic features and the presence of RF is currently used to establish a diagnosis.^1,2
• Because physical effects of early disease are often subtle, and may overlap with symptoms of other conditions, diagnosis of RA can be challenging.²
• Early diagnosis and treatment are important, as potentially irreversible joint damage occurs early in the course of disease.³

A number of criteria and composite measures are used to assess disease activity and monitor response to therapy in RA

American College of Rheumatology (ACR) criteria	Originally published in 19954 A 20% improvement in these criteria, a result that is known as ACR20, requires a 20% reduction in the number of swollen joints on a 68-joint count, in the number of tender joints on a 66-joint count and in three of five of the following criteria: Patient’s assessment of pain Patient’s global assessment of disease activity Physician’s global assessment of disease activity Patient’s assessment of physical function Markers of inflammation (e.g. erythrocyte sedimentation rate [ESR] or CRP) ACR50 and ACR70 similarly require 50% and 70% reductions, respectively5 An ACR70 response is sometimes used to refer to a state of clinical remission, although clinical remission is a status rather than a change of disease activity
Disease activity score 28 (DAS28)	Disease activity score in 28 joints – a composite numerical score which combines several discrete individual measures of RA activity, such as swollen joint count, tender joint count, ESR and measures of general health status, into a single grading of disease severity Score ranges from 0 to 10 with a higher score indicating a higher disease activity A DAS28 of <2.6 is typically used to define clinical disease remission, although other clinical definitions exist
European League Against Rheumatism response criteria	Combines the DAS28 at the time of evaluation with the change in DAS28 between two time points and may be used to define improvement or response to treatment Response categories include good, moderate and low response
Radiographic evaluation	Radiography provides an objective measure of the extent of anatomical joint damage A range of radiographic scores are currently used, many of which combine assessments of erosions and joint space narrowing – such as the Sharp score, the Larsen score and modified versions of these scores6
Health Assessment Questionnaire - Disability Index (HAQ-DI)	A standardised and widely used patient self-report questionnaire developed to assess the patient's physical function in rheumatic diseases and since applied to a wide variety of other clinical fields7 Comprises 20 questions in eight domains; the final score is the mean of the highest scores across the eight domains and ranges from 0 to 3, with higher levels reflecting greater disability8
Functional Assessment of Chronic Illness (FACIT) -Fatigue	A short (13-question) validated standard patient self-report questionnaire designed to measure fatigue and its impact on daily function9 The FACIT–Fatigue scale ranges from 0 to 52, with higher scores indicating less fatigue There is also a more detailed fatigue questionnaire called FACIT–F
Medical Outcomes Short Form-36©	A self-administered patient questionnaire validated as a measure of health-related quality of life in RA patients Comprises eight subscales (domains), which assess different aspects of patient health, and two summary scales (the physical and mental component summary scales)10

References:

1. Arnett FC, et al. The American Rheumatism Association 1987 revised criteria for the classification of rheumatoid arthritis. Arthritis Rheum 1988; 31:315–324.
2. O’Dell JR. Therapeutic strategies for rheumatoid arthritis. N Engl J Med 2004; 350:2591–2602.
3. Lindqvist E, et al. Course of radiographic damage over 10 years in a cohort with early rheumatoid arthritis. Ann Rheum Dis 2003; 62:611–616.
4. Felson DT, et al. American College of Rheumatology. Preliminary definition of improvement in rheumatoid arthritis. Arthritis Rheum 1995; 38:727–735.
5. Rindfleisch JA, Muller D. Diagnosis and management of rheumatoid arthritis. Am Fam Physician 2005; 72:1037–1047.
6. Baron G, et al. Reporting of radiographic methods in randomised controlled trials assessing structural outcomes in rheumatoid arthritis. Ann Rheum Dis 2007; 66:651–657.
7. Fries JF, et al. Measurement of patient outcome in arthritis. Arthritis Rheum 1980; 23:137–145.
8. Smolen JS, et al. Effect of interleukin-6 receptor inhibition with tocilizumab in patients with rheumatoid arthritis (OPTION study): a double-blind, placebo-controlled, randomised trial. Lancet 2008; 371:987–997.
9. Cella D, et al. Validation of the Functional Assessment of Chronic Illness Therapy Fatigue Scale relative to other instrumentation in patients with rheumatoid arthritis. Rheumatology 2005; 32:811–819.
10. Kosinski M, et al. The SF-36 Health Survey as a generic outcome measure in clinical trials of patients with osteoarthritis and rheumatoid arthritis: relative validity of scales in relation to clinical measures of arthritis severity. Med Care 1999; 37:MS23–MS39.