Recently, there is increasing evidence HMGB1 contributes to the pathogenesis of chronic inflammatory and autoimmune diseases due to its inflammatory and immune stimulating properties. Diagnosis
Laboratory tests
Antinuclear antibody (ANA) testing and anti-extractable nuclear antigen (anti-ENA) form the mainstay of serologic testing for SLE. If ANA is negative the disease can be ruled out.Several techniques are used to detect ANAs. The most widely used is indirect immunofluorescence (IF). The pattern of fluorescence suggests the type of antibody present in the peoples serum. Direct immunofluorescence can detect deposits of immunoglobulins and complement proteins in peoples skin. When skin not exposed to the sun is tested, a positive direct IF (the so-called lupus band test) is evidence of systemic lupus erythematosus.ANA screening yields positive results in many connective tissue disorders and other autoimmune diseases, and may occur in normal individuals. Subtypes of antinuclear antibodies include anti-Smith and anti-double stranded DNA (dsDNA) antibodies (which are linked to SLE) and anti-histone antibodies (which are linked to drug-induced lupus). Anti-dsDNA antibodies are highly specific for SLE; they are present in 70% of cases, whereas they appear in only 0.5% of people without SLE.Laboratory tests can also help distinguish between closely related connective tissue diseases. A multianalyte panel (MAP) of autoantibodies, including ANA, anti-dsDNA, and anti-Smith in combination with the measurement of cell-bound complement activation products (CB-CAPs) with an integrated algorithm has demonstrated 80% diagnostic sensitivity and 86% specificity in differentiating diagnosed SLE from other autoimmune connective tissue diseases.
The MAP approach has been further studied in over 40,000 patients tested with either the MAP or traditional ANA testing strategy (tANA), demonstrating patients who test MAP positive are at up to 6-fold increased odds of receiving a new SLE diagnosis and up to 3-fold increased odds of starting a new SLE medication regimen as compared to patients testing positive with the tANA approach.The anti-dsDNA antibody titers also tend to reflect disease activity, although not in all cases. Other ANA that may occur in people with SLE are anti-U1 RNP (which also appears in systemic sclerosis and mixed connective tissue disease), SS-A (or anti-Ro) and SS-B (or anti-La; both of which are more common in Sjögrens syndrome). SS-A and SS-B confer a specific risk for heart conduction block in neonatal lupus.Other tests routinely performed in suspected SLE are complement system levels (low levels suggest consumption by the immune system), electrolytes and kidney function (disturbed if the kidney is involved), liver enzymes, and complete blood count. The lupus erythematosus (LE) cell test was commonly used for diagnosis, but it is no longer used because the LE cells are only found in 50–75% of SLE cases and they are also found in some people with rheumatoid arthritis, scleroderma, and drug sensitivities. Because of this, the LE cell test is now performed only rarely and is mostly of historical significance. Diagnostic criteria
Some physicians make a diagnosis based on the American College of Rheumatology (ACR) classification criteria.