Phenotypic features and predictors of the clinical severity of keratoconjunctivitis sicca and salivary gland dysfunction in patients with Sjögren’s syndrome: a longitudinal analysis of the Korean Initiative of primary Sjögren’s Syndrome (KISS) cohort

Objective: The aim was to investigate prevalence and degree of ocular and oral involvement in patients with primary Sjögren’s syndrome (PSS). Method: We analysed 134 participants from the Korean Initiative of PSS cohort who completed a 2 year follow-up oral and ocular sign test. The severity of keratoconjunctivitis sicca (KCS) was determined with the Schirmer I test value (STV) [abnormal (AB) ≤ 5 mm/5 min; normal (N) > 5 mm/5 min]. Salivary gland dysfunction (SGD) was determined by unstimulated whole salivary (UWS) flow rate [moderate to severe (MS) < 0.1 mL/min; mild (Mi) ≥ 0.1 mL/min]. Subgroups were divided into three groups according to STV and severity of SGD: AB-STV/MS-SGD, AB-STV/Mi-SGD, and N-STV/MS-SGD groups. We analysed the changes in STV and SGD during the follow-up period. Results: Among the 134 participants enrolled in this study, 105 (78%) were placed in the AB-STV/MS-SGD group, 16 (12%) in the AB-STV/Mi-SGD, and 13 (10%) in the N-STV/MS-SGD at the 2 year follow-up. The AB-STV/Mi-SGD group was younger than the other two groups, and had a lower Xerostomia Inventory score and lower level of β ₂ -microglobulin. Participants in the N-STV/MS-SGD group had less hyperimmunoglobulinaemia, rheumatoid factor (RF), and antinuclear antibodies (ANAs). Patients and those with positive RF or ANA ≥ 1:320 at baseline were more likely to have abnormal STV at the 2 year follow-up. Conclusions: Patients with PSS and positive RF or ANA ≥ 1:320 at baseline may benefit from regular ophthalmology examinations, even if they do not have KCS at baseline or dry eye symptoms.