Matthew H. Liang

The revised criteria for the classification of rheumatoid arthritis (RA) were formulated from a computerized analysis of 262 contemporary, consecutively studied patients with RA and 262 control subjects with rheumatic diseases other than RA (non-RA). The new criteria are as follows: 1) morning stiffness in and around joints lasting at least 1 hour before maximal improvement; 2) soft tissue swelling (arthritis) of 3 or more joint areas observed by a physician; 3) swelling (arthritis) of the proximal interphalangeal, metacarpophalangeal, or wrist joints; 4) symmetric swelling (arthritis); 5) rheumatoid nodules; 6) the presence of rheumatoid factor; and 7) radiographic erosions and/or periarticular osteopenia in hand and/or wrist joints. Criteria 1 through 4 must have been present for at least 6 weeks. Rheumatoid arthritis is defined by the presence of 4 or more criteria, and no further qualifications (classic, definite, or probable) or list of exclusions are required. In addition, a "classification tree" schema is presented which performs equally as well as the traditional (4 of 7) format. The new criteria demonstrated 91-94% sensitivity and 89% specificity for RA when compared with non-RA rheumatic disease control subjects.

OBJECTIVE: To standardize outcome measures in systemic lupus erythematosus (SLE). Three indices were identified which could adequately describe outcome (disease activity, damage from disease, and health status); we describe here the development of the Disease Activity Index. METHODS: Twenty-four variables were identified as important factors in a disease activity index. These were used to generate 574 patient profiles, which were rated on a disease activity scale of 0-10 by 14 rheumatologists. A second rating of 10 of the profiles yielded scores that were not significantly different from the first, indicating that experienced clinicians can reliably make global estimates of disease activity. Multiple regression models were used to estimate the relative importance of the 24 clinical variables in the physicians' global rating of disease activity. These were estimated on a "training set" of 75% of physicians' ratings, and then validated on a "testing set," consisting of the remaining 25% of physicians' ratings. RESULTS: The explanatory power of the models in the training set was high (R2 = 0.93). The models' regression coefficients for the organ systems were simplified for easier use in clinical practice. This generated a "weighted" index of 9 organ systems for disease activity in SLE, the SLEDAI, as follows: 8 for central nervous system and vascular, 4 for renal and musculoskeletal, 2 for serosal, dermal, immunologic, and 1 for constitutional and hematologic. The maximum theoretical score is 105, but in practice, few patients have scores greater than 45. The SLEDAI predicted well the physicians' ratings in the testing set (Pearson's correlation coefficients = 0.64-0.79). CONCLUSION: The SLEDAI is a validated model of experienced clinicians' global assessments of disease activity in lupus. It represents the consensus of a group of experts in the field of lupus research.

OBJECTIVE: To provide a single source for the best available estimates of the national prevalence of arthritis in general and of selected musculoskeletal disorders (osteoarthritis, rheumatoid arthritis, juvenile rheumatoid arthritis, the spondylarthropathies, systemic lupus erythematosus, scleroderma, polymyalgia rheumatica/giant cell arteritis, gout, fibromyalgia, and low back pain). METHODS: The National Arthritis Data Workgroup reviewed data from available surveys, such as the National Health and Nutrition Examination Survey series. For overall national estimates, we used surveys based on representative samples. Because data based on national population samples are unavailable for most specific musculoskeletal conditions, we derived data from various smaller survey samples from defined populations. Prevalence estimates from these surveys were linked to 1990 US Bureau of the Census population data to calculate national estimates. We also estimated the expected frequency of arthritis in the year 2020. RESULTS: Current national estimates are provided, with important caveats regarding their interpretation, for self-reported arthritis and selected conditions. An estimated 15% (40 million) of Americans had some form of arthritis in 1995. By the year 2020, an estimated 18.2% (59.4 million) will be affected. CONCLUSION: Given the limitations of the data on which they are based, this report provides the best available prevalence estimates for arthritis and other rheumatic conditions overall, and for selected musculoskeletal disorders, in the US population.

OBJECTIVE: To develop and perform an initial validation of a damage index for systemic lupus erythematosus (SLE). METHODS: A list of items considered to reflect damage in SLE was generated through a nominal group process. A consensus as to which items to be included in an index was reached, together with rules for ascertainment. Each center submitted 2 assessments, 5 years apart, on 2 patients with active and 2 with inactive disease, of whom 1 had increased damage and the other had stable disease. Analysis of variance was used to test the factors physician, time, amount of damage, and activity status. RESULTS: Nineteen physicians completed the damage index on 42 case scenarios. The analysis revealed that the damage index could identify changes in damage seen in patients with both active and inactive disease. Patients who had active disease at both time points had a higher increase in damage. There was good agreement among the physicians on the assessment of damage in these patients. CONCLUSION: This damage index for SLE records damage occurring in patients with SLE regardless of its cause. The index was demonstrated to have content, face, criterion, and discriminant validity.

OBJECTIVE: To provide a single source for the best available estimates of the US prevalence of and number of individuals affected by arthritis overall, rheumatoid arthritis, juvenile arthritis, the spondylarthritides, systemic lupus erythematosus, systemic sclerosis, and Sjögren's syndrome. A companion article (part II) addresses additional conditions. METHODS: The National Arthritis Data Workgroup reviewed published analyses from available national surveys, such as the National Health and Nutrition Examination Survey and the National Health Interview Survey (NHIS). For analysis of overall arthritis, we used the NHIS. Because data based on national population samples are unavailable for most specific rheumatic conditions, we derived estimates from published studies of smaller, defined populations. For specific conditions, the best available prevalence estimates were applied to the corresponding 2005 US population estimates from the Census Bureau, to estimate the number affected with each condition. RESULTS: More than 21% of US adults (46.4 million persons) were found to have self-reported doctor-diagnosed arthritis. We estimated that rheumatoid arthritis affects 1.3 million adults (down from the estimate of 2.1 million for 1995), juvenile arthritis affects 294,000 children, spondylarthritides affect from 0.6 million to 2.4 million adults, systemic lupus erythematosus affects from 161,000 to 322,000 adults, systemic sclerosis affects 49,000 adults, and primary Sjögren's syndrome affects from 0.4 million to 3.1 million adults. CONCLUSION: Arthritis and other rheumatic conditions continue to be a large and growing public health problem. Estimates for many specific rheumatic conditions rely on a few, small studies of uncertain generalizability to the US population. This report provides the best available prevalence estimates for the US, but for most specific conditions, more studies generalizable to the US or addressing understudied populations are needed.