Advances and pitfalls in anti-double-stranded DNA autoantibody detection and interpretation

Figure 1 Schematic representation of Crithidia luciliae showing cellular structures relevant to Crithidia luciliae immunofluorescence test interpretation. A positive Crithidia luciliae immunofluorescence test result is defined by specific fluorescence of the kinetoplast, which contains pure double-stranded DNA (dsDNA) devoid of histones. Nuclear fluorescence may be present but is not required for a positive result. Isolated nuclear fluorescence without kinetoplast staining should be interpreted as negative for anti-dsDNA antibodies and may indicate antibodies to other nuclear antigens.

Figure 2 Proposed testing strategy for anti-double-stranded DNA autoantibodies. For the initial diagnosis of systemic lupus erythematosus (SLE), a three-step approach is recommended, beginning with clinical suspicion of SLE and a positive antinuclear antibodies (ANA) - indirect immunofluorescence with a homogeneous nuclear pattern, followed by measurement of anti-double-stranded DNA (anti-dsDNA) autoantibodies using a solid-phase immunoassay (chemiluminescence immunoassay, fluoroenzyme immunoassay, or enzyme-linked immunosorbent assay), with confirmation of positive results using the highly specific Crithidia luciliae indirect immunofluorescence test (CLIFT). Final interpretation should always integrate the clinical manifestations, ANA profile, and C3 and C4 complement levels. In patients with persistent clinical suspicion, a positive solid-phase assay with a negative CLIFT result may warrant repeat testing after 3-6 months. In patients with established SLE, disease monitoring should preferably be performed using the same assay platform. Anti-dsDNA results should always be interpreted in conjunction with clinical disease activity, serum C3 and C4 concentrations, and organ-specific assessments, particularly in patients with suspected lupus nephritis. CLIFT: Crithidia luciliae indirect immunofluorescence test; ELISA: Enzyme-linked immunosorbent assay; CLIA: Chemiluminescence immunoassay; FEIA: Fluoroenzyme immunoassay; SLE: Systemic lupus erythematosus; anti-dsDNA: Anti-double-stranded DNA; LN: Lupus nephritis; ANA: Antinuclear antibodies; IIF: Indirect immunofluorescence.