Clinical Information

Anti-double-stranded DNA (anti-dsDNA) antibodies are a hallmark serological marker for systemic lupus erythematosus (SLE), with high specificity that makes them crucial for diagnosing and classifying the disease, particularly under the 2012 Systemic Lupus International Collaborating Clinics and 2019 European Alliance of Associations for Rheumatology/American College of Rheumatology criteria.(1-3) Clinically, these antibodies are not just diagnostic but are strongly associated with disease activity and the pathogenesis of severe complications, most notably lupus nephritis (LN), as their titers often rise just before or during clinical flares.(4-7)

The frequently used methods for detection and quantification of anti-dsDNA antibody in the clinical laboratory include the solid-phase immunoassays (SPAs) such as the enzyme linked immunosorbent assay (ELISA), fluoro-enzyme immunoassay, chemiluminescence immunoassay, multiplexed bead-based assays and indirect immunofluorescence test using Crithidia luciliae (CLIFT) as substrate.(8) The Farr radioimmunoassay (RIA) is traditionally considered a "gold standard" for detecting anti-dsDNA antibody testing as it selectively detects high avidity antibodies, uses native antigen, and has high specificity. However, the Farr-RIA has largely been replaced by manual or automated solid-phase immunoassays and CLIFT.

The CLIFT is a highly specific diagnostic tool used primarily for the confirmation of medium-to-high avidity and medium-to-high affinity anti-dsDNA IgG antibodies.(3) By utilizing the kinetoplast of the non-pathogenic hemoflagellate Crithidia luciliae, which contains a dense, pure concentration of circular double-stranded DNA (dsDNA), the assay provides a unique substrate free from contaminating nuclear antigens like histones or single-stranded DNA.(8) While its sensitivity is moderate (approximately 42%-76%), its specificity for SLE is nearly 98% to 100%, making it an essential "rule-in" test after an initial positive result from more sensitive but less specific SPAs like ELISA.

Beyond its role in SLE diagnosis, the CLIFT carries significant clinical weight in assessing disease activity and organ involvement.(4,6,7) Positive results are strongly linked to active SLE and LN, and associated with complement consumption.(9,10) Because the CLIFT preferentially detects medium-to-high avidity and medium-to-high affinity IgG antibodies, a positive titer is frequently associated with periods of disease flare, whereas a negative result may occur during remission even if other assays remain positive. Consequently, clinicians use the CLIFT to assess risk for disease remission and specific clinical manifestations, as high titers often drop in response to successful immunosuppressive therapy. However, due to its high specificity but low sensitivity, the CLIFT is widely used as a confirmatory test following a positive anti-dsDNA IgG result obtained in a SPA.(4-8)

Discordant results between SPAs as well as SPAs and CLIFT for anti-dsDNA antibodies is relatively common (3-5,7-8), occurring in a fifth of patients overall and a third of visits.(7)