The American College of Rheumatology criteria for the classification of systemic lupus erythematosus: strengths, weaknesses, and opportunities for improvement.

The American College of Rheumatology classification criteria were developed to operationalize the definition of systemic lupus erythematosus (SLE) to allow comparison of clinical research from different centers, but also serve to facilitate education and to guide clinical practice. The classification criteria have been critical to research, but should be viewed as a temporary step until improved understanding of the pathogenesis of SLE emerges. Criteria have inherent limitations, including bias towards more severe and longer duration disease, equal weighting of features that vary in clinical significance, and exclusion of patients with SLE from research because they do not meet criteria. For some SLE research questions, it may be appropriate to include patients diagnosed with SLE who do not meet criteria, if these patients' manifestations and criteria are documented explicitly. SLE disease activity, cumulative organ damage, disease duration, criteria ever met, and criteria met at time of enrollment are important data that should be presented in clinical studies of SLE regardless of the number of criteria met. The criteria should be reevaluated periodically, utilizing patients and controls with a range of diseases and disease severity. A simplified weighting system may more accurately reflect clinical practice.