ANTINUCLEAR ANTIBODIES (ANA)
Detect antibodies to nuclear antigens.
The indirect immunofluorescent test has three elements to consider in the result:
1. Positive or negative fluorescence. A negative test is strong evidence against a diagnosis of SLE but not conclusive. See Anti-DNA (Single-stranded) Antibodies, Quantitative, IgG .
2. The titer (dilution) to which fluorescence remains positive (provides a reflection of the concentration or avidity of the antibody). Many individuals, particularly the elderly, may have low titer ANA without significant disease substantiated after work-up.
3. The pattern of nuclear fluorescence (reflecting specificity for various diseases). Homogenous and/or nuclear rim (peripheral) pattern correlates with antibody to native DNA and deoxynucleoprotein and bears correlation with SLE, SLE activity, and lupus nephritis. Homogenous (diffuse) pattern suggests SLE or other connective tissue diseases. Speckled pattern correlates with antibody to nuclear antigens extractable by saline; it is found in many disease states, including SLE and scleroderma. When antibodies to DNA and deoxyribonucleoprotein are present (rim and homogenous pattern), there may be interference with the detection of speckled pattern. Nucleolar pattern is seen in sera of patients with progressive systemic sclerosis and Sjögren's syndrome. Centromere pattern is seen in CREST syndrome.