Clinical usefulness of the Crithida luciliae test for antibodies to native DNA.

The Crithidia luciliae assay (CL-IF) for antibodies to native DNA was found to be significantly more sensitive and specific for systemic lupus erythematosus (SLE) than the Farr radioimmunoassay (RIA). High titers of antibodies to native DNA were seen exclusively in patients wtih SLE using the CL-IF test. The titers correlated with the activity of SLE and nephritis, in that the highest titers occurred in patients with active disease and severe nephritis, the lowest in patients with inactive lupus and normal renal function. Favorable responses to therapy were associated with decreases in CL-IF titers. The CL-IF assay can detect complement-fixing antibodies to native DNA. Their presence correlated with the disease activity and nephritis in SLE patients. The simple and inexpensive CL-IF test could either replace the RIA in clinical laboratories or be used in conjunction with the RIA as a confirmatory test for antibodies to native DNA.