Associations among classification criteria items within systemic lupus erythematosus.

Abstract

A project towards new SLE classification criteria supported by both EULAR and the ACR is based on weighted criteria that include both laboratory and clinical items. Combinations of certain symptoms may occur commonly in SLE, which would argue against independently counting these items. However, these interrelationships have not been formally investigated.To evaluate the interrelationship between candidate criteria items in an international early SLE cohort and in the Euro-Lupus cohort.The international early SLE cohort included 389 patients, who were diagnosed within the last 3 years. Data on ACR 1997, SLICC 2012 and 30 additional items were collected. To evaluate the inter-relationship of criteria, a tetrachoric correlation was used to assess the degree of association between different manifestations of the same organ-system. The correlations identified in the international early SLE cohort were validated in the Euro-Lupus cohort.A few relevant correlations were observed among specific clinical cutaneous manifestations (in particular, malar rash correlated with photosensitivity, alopecia, and oral ulcers) and serologic manifestations (anti-Sm and anti-dsDNA and anti-RNP, anti-Ro with anti-La, and between anti-phospholipid antibodies), and these results were validated in the Euro-Lupus cohort. The associations within the mucocutaneous domain, hematologic and the specific autoantibodies suggest that within a single domain only the highest ranking item should be counted to avoid overrepresentation.Some of the candidate SLE criteria do cluster within domains. Given these interrelationships, multiple criteria within a domain should not be independently counted. These results are important for the structure of new SLE classification criteria.