The clinical significance of the antinuclear antibody test as a screening procedure for DNA antibodies in SLE.

During the two-year period (1st October 1974-30th September 1976), 2979 sera were tested for DNA antibodies by the Farr test. One thousand six hundred and ninety-five of these were tested because they had high ANA titres (1/256 or greater). In this group 285 sera were found to have raised DNA binding capacities (DNA-bc), 86 of which were found in patients having diagnoses other than SLE. When the diagnoses were reviewed following the finding of a raised DNA-bc, 55 of these patients were found to be suffering from SLE. Of the 1284 sera tested for DNA antibodies without the prior ANA screening procedures, 288 were positive, 36 of which came from patients not considered to have SLE; 30 of these patients were subsequently shown to have SLE. Thus the DNA-bc test is an important tool in the diagnosis of SLE, and the ANA test appears to be a valuable screening procedure. The level of DNA-bc was not of any diagnostic value.