The UK Primary Sjögren's Syndrome Registry (UKPSSR) is a national observational cohort of clinically well-characterised patients with primary Sjögren's syndrome, who fulfil the 2002 American European Consensus Group (AECG) classification criteria. Our study cohort was recruited between Aug 13, 2009 and Sept 27, 2011.
12 The UKPSSR is an ongoing initiative. The UKPSSR holds detailed clinical and laboratory data that is collected prospectively, including patient-reported symptoms collected using standardised questionnaires.
Two independent European cohorts of patients with primary Sjögren's syndrome were used as validation cohorts: the French Assessment of Systemic Signs and Evolution of Sjögren's Syndrome (ASSESS) cohort, and the Norwegian Stavanger cohort. All patients met the 2002 AECG criteria. The ASSESS cohort is a French cohort of patients recruited from 15 tertiary centres for autoimmune diseases between 2006 and 2009. The Stavanger cohort consists patients with primary Sjögren's syndrome attending the Stavanger University Hospital (Norway), recruited between January, 2014, and August, 2016.
Baseline data that permitted our symptom-based stratification were available from two randomised, placebo-controlled trials of patients with primary Sjögren's syndrome; the JOQUER trial,
17 which investigated hydroxychloroquine treatment, and the TRACTISS trial,
18 which investigated rituximab treatment. In the JOQUER trial, 120 patients were randomly assigned (56 to hydroxychloroquine and 64 to placebo), of whom 107 had baseline data permitting symptom-based stratification. In the TRACTISS trial, 133 patients were randomly assigned (67 to rituximab and 66 to placebo), of whom 114 had baseline data permitting stratification.