Diagnosis of systemic lupus erythematosus in Jamaica by Crithidia luciliae indirect immunofluorescence test.

The Crithidia luciliae indirect immunofluorescence test (CL-IFT) was compared with the DNA-binding assay for confirmation of the presence of double-stranded DNA (dsDNA) antibodies in cases of systemic lupus erythematosus (SLE). The study involved 142 patients whose sera had anti-nuclear antibodies (ANA). In 62 patients with clinical or suspected SLE, 66% gave positive CL-IFT results as against 69% by DNA-binding. Two patients who had negative CL-IFT results but positive DNA-binding were only marginally positive (31% and 36%). Anti-dsDNA antibody was not found in any ANA negative sera. C. luciliae is easily maintained in culture and the test is relatively easy to perform in any laboratory with facilities for doing fluorescence microscopy; we recommend it for confirmation of the diagnosis of SLE, especially in laboratories with limited resources.