The detection of double stranded DNA antibody using human metaphase chromosomes

Double stranded native DNA (dsDNA) antibody detection is important in the diagnosis and management of patients with Systemic Lupus Erythematosus (SLE). Current radioimmunoassay and haemagglutination assays for DNA antibodies are technically complicated or show considerable inter-laboratory variation. A simple inexpensive indirect immunofluorescence method using fixed human metaphase chromosomes for DNA antibody estimation is described. The method has been compared with the Farr radioimmunoassay and Crithidia luciliae techniques. The metaphase test showed 100% correlation with a positive Farr assay in 38 of 373 routine DNA antibody estimations. Simultaneous testing using Crithidia showed 84% correlation, indicating greater sensitivity of the metaphase method. Enzyme treatment of metaphase and Crithidia substrate abolished reactivity on DNAase treated substrate alone, and DNA specific fluorescent staining further confirmed metaphase substrate specificity. The metaphase test appears simple, specific, of greater sensitivity, easily read, and can be utilized in large or small laboratories to determine DNA antibodies and their subclasses.