Diseases with multiple and variable manifestations always cause difficulties in making a reliable and rapid diagnosis. Systemic lupus erythematosus is not easy to diagnose. The disease often begins insidiously and is similar to other diseases due to a variety of symptoms. In any case, an internal rheumatologist should be consulted if lupus-like signs and an unclear diagnosis are present. The latter may arrange for any necessary investigations to be carried out. This requires interdisciplinary cooperation with other specialist areas such as skin, heart and kidney specialists. There is no single diagnostic finding for SLE. The diagnosis is based on clinical and serological (blood parameters) building blocks. The ACR classification criteria facilitate the classification of symptoms and findings as SLE, but they are not primary diagnostic criteria.
ACR Classification Criteria:
- Butterfly erythema (typical reddening of the face)
- discus-like skin changes, circular red skin spots
- Sensitivity to light, i.e. persistent redness of the skin as in a sun allergy
- Recurrent ulcers in the mouth (oral aphthae) without other causes
- Otherwise unexplained joint swelling (arthritis)
- pleurisy, pericarditis, or inflammation of the pericardium
- Kidney inflammation with protein and blood in the urine
- seizures or psychoses (not due to taking medication or metabolic disorders)
- Unclear persistent decrease in red or white blood cells or platelets (leukopenia or thrombopenia)
- Clear antibody tests: (Anti-dsDNA Antibodies, Anti-Sm Antibodies, Antiphospholide Antibodies)
- Positive antinuclear antibodies (ANA) that are not caused by drugs or other diseases.
In order to diagnose SLE safely, a whole range of different methods may be necessary to determine organ involvement. In addition to a comprehensive blood and urine examination, this also includes imaging diagnostics such as X-rays, sonography and MRT, ECG and echocardiography, endoscopy and capillaroscopy.
Basic laboratory tests at SLE:
- BSG, CRP
- Blood count, differential blood count
- creatinine
- Liver values, LDH
- Complements C3, C4, CH50
- Urine status (dysmorphic erythrocytes), 24 h collecting urine
General laboratory:
The increase in the blood cell lowering rate (BSR) and an increased content of various antibodies in the blood (polyclonal hypergammaglobulinemia) are expressions of a chronic inflammatory process. The C-reactive protein (CRP) is often - even with higher disease activity - only slightly elevated or of normal value. Decreases in the number of immune cells in the blood, such as leukopenia, thrombocytopenia and anemia, are often found. Circulating (auto)antibodies bind corresponding antigens and can activate and consume components of the complement system. This leads to the decrease of certain complement factors in the blood (C3- and C4-lowering) and is interpreted as a sign of disease activity.
Immunological diagnostics:
Typical of SLE is the production of a number of autoantibodies. While the detection of antinuclear antibodies (ANA) is almost always successful, but relatively non-specific, antibodies against double-stranded DNA (dsDNA-AK), antibodies against the Smith antigen, are far more specific for the
SLE. Other antibodies can be: ssDNA, histone-AK, SSA-AK, SSB-AK.
Urinalysis:
The detection of so-called proteinuria (protein excretion in urine) should result in further analysis. The detection of dysmorphic (deformed) erythrocytes and protein in the urine can speak for a co-participation of the kidneys.
