From the Guidelines
Lupus diagnosis should be based on the European League Against Rheumatism (EULAR) and the American College of Rheumatology (ACR) 2019 classification criteria, which require a positive antinuclear antibody (ANA) test result at a titer ≥1:80 by indirect immunofluorescence on HEp-2 cells, along with other specific clinical and immunologic criteria. The EULAR/ACR 2019 criteria are considered a simple, direct, and precise classification method that can be easily implemented and integrated into computer applications 1. These criteria have been developed through a balanced use of both expert-based and data-driven methods, and their sensitivity and specificity are superior to all previously published classification criteria 1.
The key clinical criteria for lupus diagnosis include:
- Malar rash (butterfly-shaped rash across the cheeks)
- Discoid rash
- Photosensitivity
- Oral ulcers
- Arthritis
- Serositis (inflammation of body cavities)
- Renal disorder
- Neurologic disorder
- Hematologic disorder (blood abnormalities)
Laboratory criteria for lupus diagnosis include:
- Positive antinuclear antibody (ANA)
- Anti-double stranded DNA antibodies
- Anti-Smith antibodies
- Antiphospholipid antibodies
- Low complement levels
- Direct Coombs test
It is essential to note that no single test can diagnose lupus, and doctors must evaluate symptoms, physical examination findings, and laboratory results collectively 1. The use of ANA detection as an entry criterion in the SLE classification can be considered a strategic move, but it is necessary to insist that this is a classification criterion of limited use in diagnosing or screening 1.
In clinical practice, ANA tests are requested in various scenarios, such as diagnosis, clinical algorithms to rule out autoimmune disorders, and treatment evaluation unrelated to SLE 1. The relatively low specificity of ANA detection reflects the fact that ANA are associated with a variety of systemic rheumatologic disorders and are relatively frequent in healthy individuals 1.
Early diagnosis is crucial for proper management, as lupus can affect multiple organ systems and varies greatly in severity between individuals. Diagnosis often requires consultation with a rheumatologist who specializes in autoimmune diseases. The correct application of the classification criteria is essential, and maximum attention must be put into the interpretation of laboratory test results, including the use of international units (IU) and likelihood ratios 1.
From the Research
Criteria for Diagnosing Lupus
The diagnosis of lupus, also known as systemic lupus erythematosus (SLE), is based on a combination of clinical and laboratory criteria. Some of the key criteria include:
- Presence of anti-double stranded DNA (anti-dsDNA) antibodies, which are highly specific markers of SLE 2, 3, 4, 5
- Antinuclear antibody (ANA) screening, which can help identify patients with SLE 3
- Clinical manifestations such as skin rashes, joint pain, and kidney damage 4, 6
- Disease activity, which can be measured using various indices such as the SLE Disease Activity Index (SLEDAI) and the Systemic Lupus Activity Measure (SLAM) 6
Laboratory Tests
Several laboratory tests can be used to diagnose lupus, including:
- Enzyme-linked immunosorbent assay (ELISA) for anti-dsDNA antibodies 2, 3, 5, 6
- Crithidia luciliae fluorescence test (CLIFT) for anti-dsDNA antibodies 3, 6
- Indirect immunofluorescence assay (ANA-IIFA) for ANA screening 3
- Fluorescence immunoassay (ELiA dsDNA) for anti-dsDNA antibodies 5
Disease Activity and Anti-dsDNA Antibodies
Research has shown that changes in anti-dsDNA antibody levels can be associated with changes in disease activity in patients with SLE. For example:
- A concurrent decrease in anti-dsDNA levels has been associated with higher flare rates in patients with SLE 6
- A previous increase in anti-dsDNA levels has been associated with higher flare rates in patients with SLE 6
- Anti-dsDNA antibody levels can fluctuate with disease activity in patients with SLE 2, 4