Anti-histone antibody is an important immunological marker for the diagnosis of drug induced lupus (DIL). Although anti-histone antibodies are detected in approximately 30% to 60% of patients with systemic lupus erythematosus (SLE), their presence is much higher in DIL patients. They are detected in about 95% of DIL patients, which is more important diagnostically. DIL is clinically similar to SLE, except that the former patients do not have kidney or central nervous system involvement. In addition, DIL patients do not demonstrate the multiple types of antinuclear antibodies (ANAs) often found in SLE patients.
Autoimmune ELISA kits measure autoimmune antibodies in the serum. It is based on the principle of a solid phase enzyme-linked immunosorbent assay. The assay utilizes a specific antigen for immobilization on the microtiter wells and anti-human IgG antibody conjugated to horseradish peroxidase (HRP) for detection. The test sample is allowed to react simultaneously with the two components, resulting in autoimmune antibodies being sandwiched between the solid phase antigen and the enzyme-linked antibodies. After incubation, the wells are washed to remove unbound antibodies. Then an HRP substrate is added to develop a blue color. The color development is stopped with the addition of Stop Solution changing the color to yellow. The concentration of autoimmune antibodies is directly proportional to the color intensity of the test sample. Absorbance is measured spectrophotometrically at 450 nm.