Tests
Diagnosis is made by the clinical evaluation of physical signs and symptoms and from x-rays. The following laboratory tests are also useful in the diagnosis of SLE.
Laboratory tests
- Autoantibody testing, such as:
- Anti-nuclear antibody (ANA) – is positive in almost all people with SLE
- Anti-Sm antibody – usually seen only in those with SLE
- Anti-double stranded DNA (Anti-dsDNA) – high results are characteristic of active SLE
- Anti-SSA and Anti-SSB – may also be positive
- Anti-chromatin antibodies – may be present in people with SLE who are positive for ANA but negative for anti-dsDNA
- Urinalysis – may show blood, casts, or protein
- Complete blood count (CBC) – anemia with decrease of white blood cells and platelets
- Rheumatoid factor (RF) – may be positive or negative
- Serum protein electrophoresis (SPEP) – increased gamma globulin proteins
- Sed rate (ESR) – increased with inflammation
- C-reactive protein – is elevated
- VDRL – test for syphilis may be falsely positive
- Cryoglobulin – frequently positive; cryoglobulins are abnormal proteins in the blood that will precipitate when the body temperature drops below normal, causing blockage of the blood vessels. The test involves collecting blood and cooling it in the laboratory, then checking for the presence of the precipitate or solid substance.
- Complement 3 (C-3) – often decreased; C-3 is one of nine major complement proteins associated with some diseases. Decreased amounts may be associated with lupus, gram-negative septicemia, and shock, as well as malaria.
- Blood clotting studies such as PTT – presence of autoantibodies may inhibit normal clotting function.
Non-laboratory tests
- X-ray – may be ordered to detect inflammation in the chest cavity
