What are the diagnostic criteria for Systemic Lupus Erythematosus (SLE) and Systemic Sclerosis (SSc)?

From the Guidelines

Lupus and scleroderma are autoimmune diseases with distinct diagnostic criteria, and for lupus, the 2019 EULAR/ACR classification criteria require a positive ANA test at a titer ≥1:80, while for scleroderma, skin thickening proximal to the metacarpophalangeal joints is the major criterion. The diagnostic criteria for lupus, also known as systemic lupus erythematosus, have been updated in the 2019 EULAR/ACR classification criteria, which require a positive antinuclear autoantibody (ANA) test at a titer ≥1:80 by the indirect immunofluorescence test on HEp-2 cells (IFI) as an entry criterion 1. This change has improved the performance of the criteria as a classification system, but it makes caution necessary when they are used in the diagnosis of SLE because, with the 1:80 cut-off point, ANA detection specificity for SLE is 74.7% (IC 95%: 66.7% - 81.3%) 1. For scleroderma, also known as systemic sclerosis, the diagnosis centers on skin thickening proximal to the metacarpophalangeal joints, which is the major criterion, and minor criteria include sclerodactyly, digital pitting scars or loss of finger pad tissue, and bibasilar pulmonary fibrosis 1. The 2013 ACR/EULAR classification includes skin thickening of fingers extending proximal to the metacarpophalangeal joints as sufficient for diagnosis, or a point system based on skin thickening of fingers, fingertip lesions, telangiectasia, abnormal nailfold capillaries, pulmonary arterial hypertension or interstitial lung disease, Raynaud's phenomenon, and scleroderma-related autoantibodies. Some key points to consider in the diagnosis of lupus and scleroderma include:

• The use of ANA tests as an entry criterion for lupus classification, with a titer ≥1:80 by IFI on HEp-2 cells 1
• The importance of skin thickening proximal to the metacarpophalangeal joints as the major criterion for scleroderma diagnosis 1
• The use of laboratory tests, such as complete blood count, comprehensive metabolic panel, urinalysis, and specific autoantibody tests like ANA, anti-dsDNA, and anti-Scl-70, to support the diagnosis of both conditions
• The potential need for imaging and biopsies to confirm the diagnosis of lupus and scleroderma. It is essential to note that the diagnosis of lupus and scleroderma requires a comprehensive approach, considering both clinical and laboratory findings, and that the use of classification criteria should be done with caution, taking into account the potential limitations and pitfalls of these criteria 1.

From the Research

Diagnostic Criteria for Lupus

• The American College of Rheumatology (ACR) criteria for systemic lupus erythematosus (SLE) include clinical manifestations such as skin lesions, arthritis, renal disorder, neurologic disorder, hematologic changes, and serum anti-nuclear antibody, anti-ds-DNA antibody, and anti-Sm antibody 2.
• The Systemic Lupus Collaborating Clinics (SLICC) proposed new criteria for SLE in 2012, which include the importance of low complement and new knowledge of autoantibodies 2.
• Anti-double stranded DNA (anti-dsDNA) antibodies are highly specific markers of SLE and can be detected using various methods, including enzyme-linked immunosorbent assay (ELISA) and Crithidia luciliae fluorescence test (CLIFT) 3, 4.
• A combined detection strategy based on ELISA, CLIFT, and antinuclear antibody (ANA) screening can improve the clinical relevance of anti-dsDNA antibodies in SLE diagnosis 3.

Diagnostic Criteria for Scleroderma

• There are no research papers provided to assist in answering the question about diagnostic criteria for scleroderma.

Comparison of Diagnostic Methods for Lupus

• Different studies have compared the performance of various anti-dsDNA antibody assays, including ELISA and CLIFT, and found that they have high specificity but varying sensitivity 3, 4.
• The choice of diagnostic method may depend on the clinical context and the availability of resources, and a combined approach may be necessary to improve diagnostic accuracy 3, 4.
• The correlation between anti-dsDNA antibody levels and disease activity in SLE patients has been investigated, and some studies have found a positive correlation between anti-dsDNA concentrations and CRP concentrations or a mild-to-moderate inverse correlation between concentrations of anti-dsDNA and complement C4 4.