Distinct clinical characteristics of anti-Ro/SSA-negative primary Sjögren's syndrome: data from a nationwide cohort for Sjögren's syndrome in Korea.

Objectives: To investigate clinical characteristics of patients with primary Sjögren's syndrome (SS) who were negative for anti-Ro/SSA antibody but positive for minor salivary gland biopsy (MSGB) compared to patients who presented positivity for anti-Ro/SSA antibody.
Methods: The data of 355 patients from the Korean Initiative of primary Sjögren's Syndrome (KISS), a nationwide prospective cohort for primary SS in Korea, were analysed. All patients fulfilled the 2016 American College of Rheumatology/European League Against Rheumatism (EULAR) classification criteria. Of these patients, 326 were positive for anti-Ro/SSA antibody and 29 were antibody-negative, although they had positive findings in MSGB. Various clinical features including all kinds of tests for evaluating secretory function, disease-related clinical indices and serological values available in the cohort were compared between the two groups.
Results: The anti-Ro/SSA-negative group showed less rheumatoid factor positivity (p<0.001), leucopenia (p=0.003), hyper-gammaglobulinaemia (p<0.001), lower serum β2-microglobulin level (p=0.034), more anti-centromere antibody positivity (p<0.001), higher score in dryness domain of EULAR SS patient-reported index (p=0.048) and more positivity for peripheral nervous system domain in EULAR SS disease activity index and loss of teeth in SS disease damage index (p=0.021 and 0.041, respectively) than patients who were positive for anti-Ro/ SSA antibody.
Conclusions: Primary SS patients who are negative for anti-Ro/SSA antibody have different clinical characteristics compared to patients who are positive for such antibody in Korea. Therefore, clinicians should consider MSGB in patients with suspicious symptoms who are anti-Ro/SSA-negative.