Objective
To compare the accuracy of existing classification criteria for the diagnosis of psoriatic arthritis (PsA) and to construct new criteria from observed data.

Methods
Data were collected prospectively from consecutive clinic attendees with PsA and other inflammatory arthropathies. Subjects were classified by each of 7 criteria. Sensitivity and specificity were compared using conditional logistic regression analysis. Latent class analysis was used to calculate criteria accuracy in order to confirm the validity of clinical diagnosis as the gold standard definition of “case”-ness. Classification and Regression Trees methodology and logistic regression were used to identify items for new criteria, which were then constructed using a receiver operating characteristic curve.

Results
Data were collected on 588 cases and 536 controls with rheumatoid arthritis (n = 384), ankylosing spondylitis (n = 72), undifferentiated arthritis (n = 38), connective tissue disorders (n = 14), and other diseases (n = 28). The specificity of each set of criteria was high. The sensitivity of the Vasey and Espinoza method (0.97) was similar to that of the method of McGonagle et al (0.98) and greater than that of the methods of Bennett (0.44), Moll and Wright (0.91), the European Spondylarthropathy Study Group (0.74), and Gladman et al (0.91). The CASPAR (ClASsification criteria for Psoriatic ARthritis) criteria consisted of established inflammatory articular disease with at least 3 points from the following features: current psoriasis (assigned a score of 2; all other features were assigned a score of 1), a history of psoriasis (unless current psoriasis was present), a family history of psoriasis (unless current psoriasis was present or there was a history of psoriasis), dactylitis, juxtaarticular new bone formation, rheumatoid factor negativity, and nail dystrophy. These criteria were more specific (0.987 versus 0.960) but less sensitive (0.914 versus 0.972) than those of Vasey and Espinoza.

Conclusion
The CASPAR criteria are simple and highly specific but less sensitive than the Vasey and Espinoza criteria.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/art.21972

Classification criteria for psoriatic arthritis: Development of new criteria from a large international study

Objective: To validate and refine two sets of candidate criteria for the classification/diagnosis of axial spondyloarthritis (SpA). Methods: All Assessment of SpondyloArthritis international Society (ASAS) members were invited to include consecutively new patients with chronic (⩾3 months) back pain of unknown origin that began before 45 years of age. The candidate criteria were first tested in the entire cohort of 649 patients from 25 centres, and then refined in a random selection of 40% of cases and thereafter validated in the remaining 60%. Results: Upon diagnostic work-up, axial SpA was diagnosed in 60.2% of the cohort. Of these, 70% did not fulfil modified New York criteria and, therefore, were classified as having “non-radiographic” axial SpA. Refinement of the candidate criteria resulted in new ASAS classification criteria that are defined as: the presence of sacroiliitis by radiography or by magnetic resonance imaging (MRI) plus at least one SpA feature (“imaging arm”) or the presence of HLA-B27 plus at least two SpA features (“clinical arm”). The sensitivity and specificity of the entire set of the new criteria were 82.9% and 84.4%, and for the imaging arm alone 66.2% and 97.3%, respectively. The specificity of the new criteria was much better than that of the European Spondylarthropathy Study Group criteria modified for MRI (sensitivity 85.1%, specificity 65.1%) and slightly better than that of the modified Amor criteria (sensitivity 82.9, specificity 77.5%). Conclusion: The new ASAS classification criteria for axial SpA can reliably classify patients for clinical studies and may help rheumatologists in clinical practice in diagnosing axial SpA in those with chronic back pain. Trial registration number: NCT00328068.

https://ard.bmj.com/content/annrheumdis/68/6/777.full.pdf

The development of Assessment of SpondyloArthritis international Society classification criteria for axial spondyloarthritis (part II): validation and final selection

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 or 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.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/1529-0131%28199805%2941%3A5%3C778%3A%3AAID-ART4%3E3.0.CO%3B2-V

Estimates of the prevalence of arthritis and selected musculoskeletal disorders in the United States

Objective To evaluate new classifi cation criteria for peripheral spondyloarthritis (SpA) in patients with SpA with peripheral manifestations only. Methods In this Assessment of SpondyloArthritis international Society (ASAS) study, two prespecifi ed sets of criteria were compared against the European Spondylarthropathy Study Group (ESSG) and Amor criteria in newly referred consecutive patients with undiagnosed peripheral arthritis, and/or enthesitis, and/ or dactylitis that usually began before 45 years of age. The clinical diagnosis (SpA vs no SpA) made by the ASAS rheumatologist served as reference standard. Results In all, 24 ASAS centres included 266 patients, with a fi nal diagnosis of SpA being made in 66.2%. After adjustments a fi nal set of criteria showed the best balance between sensitivity (77.8%) and specifi city (82.9%): arthritis and/or enthesitis and/or dactylitis plus (A) one or more of the following parameters: psoriasis, infl ammatory bowel disease, preceding infection, human leucocyte antigen B27, uveitis, sacroiliitis on imaging, or (B) two or more other parameters: arthritis, enthesitis, dactylitis, infl ammatory back pain in the past, family history of SpA. The new criteria performed better than modifi ed versions of the ESSG (sensitivity 62.5%, specifi city 81.1%) and the Amor criteria (sensitivity 39.8%, specifi city 97.8%), particularly regarding sensitivity. In the entire ASAS population of 975 patients the combined use of ASAS criteria for axial SpA and ASAS criteria for peripheral SpA also had a better balance (sensitivity 79.5%, specifi city 83.3%) than the modifi ed ESSG (sensitivity 79.1%, specifi city 68.8%) and Amor criteria (sensitivity 67.5%, specifi city 86.7%), respectively. Conclusions The new ASAS classifi cation criteria for peripheral SpA performed well in patients presenting with peripheral arthritis, enthesitis and/or dactylitis.

https://ard.bmj.com/content/annrheumdis/70/1/25.full.pdf

The Assessment of SpondyloArthritis international Society classification criteria for peripheral spondyloarthritis and for spondyloarthritis in general

The field of spondyloarthritis (SpA) has experienced major progress in the last decade, especially with regard to new treatments, earlier diagnosis, imaging technology and a better definition of outcome parameters for clinical trials. In the present work, the Assessment in SpondyloArthritis international Society (ASAS) provides a comprehensive handbook on the most relevant aspects for the assessments of spondyloarthritis, covering classification criteria, MRI and x rays for sacroiliac joints and the spine, a complete set of all measurements relevant for clinical trials and international recommendations for the management of SpA. The handbook focuses at this time on axial SpA, with ankylosing spondylitis (AS) being the prototype disease, for which recent progress has been faster than in peripheral SpA. The target audience includes rheumatologists, trial methodologists and any doctor and/or medical student interested in SpA. The focus of this handbook is on practicality, with many examples of MRI and x ray images, which will help to standardise not only patient care but also the design of clinical studies.

/pdf/the-assessment-of-spondyloarthritis-international-society-vscj58r79v.pdf

The Assessment of SpondyloArthritis international Society (ASAS) handbook: a guide to assess spondyloarthritis

Classification criteria for most of the disorders belonging to the spondylarthropathy group already exist. However, the spectrum of spondylarthropathy is wider than the sum of these disorders suggests. Seronegative oligoarthritis, dactylitis or polyarthritis of the lower extremities, heel pain due to enthesitis, and other undifferentiated cases of spondylarthropathy have been ignored in epidemiologic studies because of the inadequacy of existing criteria. In order to define classification criteria that also encompass patients with undifferentiated spondylarthropathy, we studied 403 patients with all forms of spondylarthropathy and 674 control patients with other rheumatic diseases. The diagnoses were based on the local clinical expert's opinion. The 403 patients included 168 with ankylosing spondylitis, 68 with psoriatic arthritis, 41 with reactive arthritis, 17 with inflammatory bowel disease and arthritis, and 109 with unclassified spondylarthropathy. Based on statistical analysis and clinical reasoning, we propose the following classification criteria for spondylarthropathy: inflammatory spinal pain or synovitis (asymmetric or predominantly in the lower limbs), together with at least 1 of the following: positive family history, psoriasis, inflammatory bowel disease, urethritis, or acute diarrhea, alternating buttock pain, enthesopathy, or sacroiliitis as determined from radiography of the pelvic region. These criteria resulted in a sensitivity of 87% and a specificity of 87%. The proposed classification criteria are easy to apply in clinical practice and performed well in all 7 participating centers. However, we regard them as preliminary until they have been further evaluated in other settings.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/art.1780341003

Huitfeldt B

Papers

The European spondylarthropathy study group preliminary criteria for the classification of spondylarthropathy