Comparison of antinuclear antibody and other immunohematological profiles among primary Sjögren's syndrome, secondary Sjögren's syndrome associated with rheumatoid arthritis or systemic lupus erythematosus, and corresponding systemic disease.

Sjögren's syndrome (SS) is currently classified into two groups (primary and secondary), because of differences in the disease in the two groups. We determined antinuclear antibody and other immunohematological parameters by using newer, more sensitive serologic methods on patients with primary SS, or secondary SS associated with rheumatoid arthritis (RA) or systemic lupus erythematosus (SLE), and patients with just the systemic disease free of SS. This study defined both distinctive and common features between primary SS and each systemic disease: High titers of fluorescent antinuclear antibodies (FANAs), anti-SS-A/SS-B antibodies, and rheumatoid factors (RFs), as well as leukocytopenia were considered the main features of primary SS. Elevated levels of RFs and C-reactive protein were prominent in RA patients. In contrast, high titers of FANAs and anti-single stranded or anti-double stranded DNA antibodies, positive anti-ribonucleoprotein or Sm antibodies, leukocytopenia, and hypocomplementemia were characteristic for SLE. Furthermore, patients with secondary SS plus RA or SLE were found to have mixed features of SS and the associated systemic disease. The results strongly suggest that patients with secondary SS have two separate diseases, SS and the associated systemic disease.