The ACR/EULAR Classification Criteria for Systemic Sclerosis (SSc)

CRA Abstracts, Canadian Rheumatology Association (CRA) Annual Scientific Meeting, Ottawa, Canada, 2013, The Journal of Rheumatology, 40, 951

Janet Pope (University of Western Ontario, London); Dinesh Khanna (University of Michigan, Ann Arbor); Jaap Fransen (University Medical Centre Nijmegen, Netherlands); Sindhu Johnson (Toronto Scleroderma Program, Toronto Western Hospital, Mount Sinai Hospital, University of Toronto, Toronto); Murray Baron (McGill University and Jewish General Hospital, Montreal); Alan Tyndall (University Hospital and Felix Platter Spital, Basel); Marco Matucci-Cerinic (Instituto di Clinica, Florence); Raymond Naden (National Women''s Hospital, Auckland); Frank van den Hoogen (Sint Maartenskliniek, Maartens)

Objective:

A joint EULAR and ACR committee was established to develop new classification criteria for SSc.

Methods:

A nominal group technique were used to create potential items for SSc classification. The validity was tested in databases of SSc cases and controls. Next, twenty cases were prospectively collected to represent the spectrum of SSc (low probability to high probability) which were ranked by SSc experts. Conjoint analysis (1000minds®) was used to assign weights to the items resulting in 17 items in 13 domains. Experts agreed that all patients with sclerodactyly and scleroderma skin involvement proximal to the MCPs were considered SSc; patients with skin involvement due another scleroderma-like disorder (e.g. scleromyxedema) were excluded. A threshold was established to classify definite SSc based on the sum of weights of 17 items. To test the algorithm, data on the items were prospectively collected in cases and controls. To refine the threshold, a subset of cases (n=25) within the range of borderline probability of SSc was selected from the collected data. Experts were then asked to determine whether each case had ‘definite SSc’ or not, leading to a new threshold. During a face-to-face meeting of the Steering Committee, the 17 items were reduced to 9 while maintaining adequate sensitivity and specificity, tested in a random sample of cases and controls of 100 from North America and 100 from Europe (derivation sample). Cases of SSc and mimickers were collected at several sites in NA and Europe where approximately half of SSc had early disease. Weights were simplified by dividing each weight by 5 and rounding to the nearest whole number. The data were then reanalyzed in the remaining cases and controls (validation set; n=405).

Results:

Mimickers of SSc need to be excluded. If sclerodactyly with involvement proximal to MCPs then SSc is classified. Otherwise, only the maximum score in each domain is counted (skin: puffy fingers=2 or sclerodactyly entire fingers=4, finger tip ulcers=2 or digital pits=3, telangiectasia=2, nailbed abnormal capillaries=2, PAH or ILD=2, RP=3, SSc antibody (centromere, topo1, RNApol3)=3. Nine or more (out of 19) had a sensitivity of 91% and specificity of 92% in the validation cohort (n=405). The sensitivity and specificity of the former 1980 ARA criteria in this database were 75% and 72%, respectively.

Conclusion:

The ACR/EULAR classification criteria for SSc performed better than 1980 Preliminary ARA Criteria for SSc. These criteria can be endorsed for epidemiological studies and clinical trials

Source: http://rheum.ca/images/documents/2013_Abstracts_Selected_for_Oral_Presentation.pdf