Lupus erythematosus cell preparation, antinuclear factor and antideoxyribonucleic acid antibody incongruity in systemic lupus erythematosus.

'Total antinuclear antibody' (ANF) is detected by the fluorescent antinuclear antibody technique which is a screening test, positive in 99% of systemic lupus erythematosus (SLE) sera. The LE factor (positive in 75% of SLE sera), like the anti-DNA antibody, is an antinuclear antibody but directed against DNA-histone. ANF-negative SLE is a clinical entity with absence of these antibodies. A false negative ANF, in the presence of high titre anti-DNA antibody and/or LE cells, is illustrated in two cases of SLE. Postulated mechanisms for this phenomenon are interference in ANF detection by rheumatoid factor, and the prozone effect on the immunofluorescent tests.