Diagnostic Approach to Systemic Lupus Erythematosus using Crithidia luciliae Immunofluorescence Test

Introduction to Crithidia luciliae Immunofluorescence Test

The Crithidia luciliae immunofluorescence test (CLIFT) is a highly specific method for detecting anti-double-stranded DNA (anti-dsDNA) antibodies, and should be used as a confirmatory test following positive solid-phase assays in the diagnostic workup of systemic lupus erythematosus (SLE), as recommended by the American College of Rheumatology 1, 2

The CLIFT offers the highest specificity for SLE among anti-dsDNA detection methods, approaching 98-100% in healthy controls and patients without autoimmune disease, according to the European League Against Rheumatism 3
Anti-dsDNA testing should follow a double-screening strategy: first-line testing with a last-generation solid-phase assay (SPA), followed by CLIFT as the confirmatory test, as suggested by the American College of Rheumatology 4, 5

When both tests are positive (SPA+ and CLIFT+), SLE is very likely, providing the highest diagnostic confidence, as stated by the American College of Rheumatology 1
When SPA is positive but CLIFT is negative (SPA+ and CLIFT-), evaluate in the context of clinical characteristics, and SLE is possible but less certain, according to the European League Against Rheumatism 1

For monitoring established SLE, a quantitative assay (such as ELISA/FEIA) should be used to monitor disease activity, preferably using the same method and laboratory used at diagnosis, as recommended by the American College of Rheumatology 1, 2, 4
CLIFT provides only semiquantitative information and should not be the sole monitoring method, according to the European League Against Rheumatism 1, 2, 5

Anti-dsDNA antibodies are heterogeneous and can target various DNA structures, including single-stranded DNA, Z-DNA, B-DNA, RNA, and DNA-histone complexes, as noted by the American College of Rheumatology 7
Anti-dsDNA positivity can occur in healthy individuals, other autoimmune diseases, infections, and malignancies, and results must always be interpreted in conjunction with clinical findings and other laboratory tests, as stated by the European League Against Rheumatism 7, 6