Antibodies against DNA are distinguished into two different types: antibodies against double stranded, native DNA (dsDNA) and antibodies against single-stranded, denatured DNA. The dsDNA-speicific antibodies (anti-dsDNA) are considered a specific marker for systemic lupus erythematosus (SLE), due to the high clinical associations [1-3]. The presence of these autoantibodies could be virtually diagnostic for SLE [1, 3]. In fact, anti-dsDNA antibodies may be present in patients even before they develop clinical features of SLE [2, 4]. Therefore, monitoring the condition of anti-dsDNA antibodies is essential for maintaining the healthy condition as well as identifying the progression of SLE. Moreover, the identification of anti-dsDNA antibodies in other pathological conditions and in healthy subjects is very rare (less than 0.5%) [3].

This assay is a quantitative sandwich ELISA. The immunoplate is pre-coated with a polyclonal antibody specific for human A1AT. Standards and samples are pipetted into the wells and any human A1AT present is bound by the immobilized antibody. After washing away any unbound substances, a horseradish peroxidase (HRP)-linked polyclonal antibody specific for human A1AT is added to the wells. After a final wash step, an HRP substrate solution is added and colour develops in proportion to the amount of human A1AT bound initially. The assay is stopped and the optical density of the wells determined using a microplate reader. Since the increases in absorbance are directly proportional to the amount of captured human A1AT, the unknown sample concentration can be interpolated from a reference curve included in each assay

A. Typical representation of standard curve
The following standard curve is provided for demonstration only. A standard curve should be generated for each set of sample assay. 

1. Qian LL, Wu L, Zhang L, Zhang J, Zhou J, Li YH, Fang QC, Li HT, Jia WP. Serum biomarkers combined with ultrasonography for early diagnosis of non-alcoholic fatty liver disease confirmed by magnetic resonance spectroscopy. Acta Pharmacologica Sinica. 2020 Apr;41(4):554-60.