Anti-La (SS-B): a diagnostic criterion for Sjögren's syndrome?

We examined the diagnostic sensitivity and specificity of antibodies to Ro (SS-A) and La (SS-B) in Sjögren's syndrome (SS) by counterimmunoelectrophoresis and immunodiffusion. Anti-Ro was found in 56% and anti-La in 42% of patients with SS and in 38% and 6% respectively in SLE. Anti-La was rare (less than 1%) in other connective tissue diseases. As a more stringent test of diagnostic specificity, 88 patients whose sera contained anti-La and/or anti-Ro were carefully examined for evidence of Sjögren's syndrome. Of 35 patients whose sera contained anti-La, 29 (83%) fulfilled criteria for SS, and four out of 6 of the remainder showed some evidence of early disease. Of 53 patients with anti-Ro (without anti-La), only 42% had Sjögren's syndrome, 45% had SLE and 13% other connective tissue diseases. These data confirm that anti-La, but not anti-Ro, has a high diagnostic specificity for Sjögren's syndrome and merits inclusion as separate diagnostic criterion for the disease.