Antiperinuclear factor in Sjögren's syndrome in the presence or absence of rheumatoid arthritis.

Serum from 91 patients with Sjögren's syndrome (SS) was examined for antiperinuclear factor (APF). Nine out of 29 patients with SS alone (31.0%) were positive as opposed to 27 out of 40 with SS + rheumatoid arthritis (67.5%) and to 3 out of 22 with SS + other autoimmune disorders (13.6%). A clear relationship was established between APF and agglutinating or non-agglutinating rheumatoid factor.