Researchers Explore Application of Standard Definition of Systemic Lupus Erythematosus in a Swedish patient population

Christopher Sjöwall from the Rheumatology/AIR Department of Clinical and Experimental Medicine at Linköping in Sweden and colleagues, evaluated the performance of the Systemic Lupus International Collaborating Clinics (SLICC) criteria created in 2012 (SLIC-12) in a European population of patients with systemic lupus erythematosus (SLE).

The study entitled, “Application of the 2012 systemic lupus international collaborating clinics classification criteria on a Regional Swedish systemic lupus erythematosus Register,” was recently published in the journal Arthritis Research & Therapy.

Systemic lupus erythematosus (SLE) is a heterogeneous disease with the most common symptoms including manifestations from joints, skin, mucous membranes, bone marrow and kidneys. Furthermore, subtle manifestations such as neurological symptoms occur and may remain unrecognized or found to be not related to SLE. The heterogeneity of SLE causes problems regarding diagnostic accuracy in clinical practice and particularly in clinical research.

Over the years, different classification criteria were created to classify SLE and differentiate it from other rheumatic diseases. The American College of Rheumatology (ACR) classification criteria from 1982 (ACR-82) have been extensively used, however, ACR-82 does not consider lowered complement levels, but includes the positive LE cell test as well as the positive Wassermann reaction (false positive serological test for syphilis) test as a part of the 10th criterion (immunologic disorder), although these tests are in general regarded obsolete. In addition, ACR-82 does not consider many of the common cutaneous and neurological manifestations found in SLE, and will not accept biopsy-proven lupus nephritis (LN) as SLE in the absence of other manifestations.

Fries & Holman’s “diagnostic principle” has been found reliable. Fries is based on the presence of ANA on at least one occasion plus signs of systemic disease with involvement of at least two defined organ systems (including skin, joints, kidney, serosa, blood, lungs, and nervous system).

With the aim of improving the ACR criteria, the Systemic Lupus International Collaborating Clinics (SLICC) network presented and validated a new set of classification criteria (SLICC-12) based on the evaluation of almost 1,400 patients. Although SLICC-12 can offer a higher sensitivity for SLE compared to previous classification grounds, studies are necessary to comprehend this diagnostic criteria sensitivity compared to previous classifications.

In this regard, in order to apply the SLICC-12 criteria, and to compare them with ACR-82, ACR-97, and Fries & Holman’s diagnostic principle, Christopher Sjöwall and colleagues assessed 243 patients with SLE according to the 1982 American College of Rheumatology (ACR-82) criteria and/or the Fries criteria. Furthermore, the study included 55 controls with suspected systemic autoimmune disease, due to presence of SLE-related autoantibody.

Results revealed that the new SLICC-12 criteria had a diagnostic sensitivity of 94% when compared to the ACR-97 criteria that only reached a sensitivity of 90%. The ACR-82 criteria was unable to identify fifth true SLE cases.

Nonetheless, SLICC-12 criteria was only able to specify 74% of SLE cases and did not modify when diagnosis of systemic disease required the involvement of at least two different organs. Furthermore, the new SLICC-12 criteria misclassified more of the controls SLE cases than the ACR-82, the ACR-97 and the Fries.

This study was the first to examine the new SLICC-12 criteria on an adult European population. Based on the results, the researchers concluded that although this new criteria is able to provide a good diagnostic sensitivity, the establishment of a standard definition remains a challenge for clinicians and researchers of the lupus disease. The team of researchers suggest that in order to achieve better results of sensitivity and specificity it is required a combination of criteria set for clinical SLE studies.