Background Primary Sjögren's Syndrome (pSS) is a chronic multi-system disease causing a wide-range of symptoms including dryness, pain and fatigue.1,2 Individual experiences of pSS differ considerably resulting in a heterogeneous patient population.3 These differences in disease-manifestation have not yet been characterised and the biological basis of varied patient-reported outcomes remains unclear.
Objectives We aim to identify distinct clinical phenotypes within pSS, using patient-reported symptoms and to determine whether such clinical subgroups display differences in healthy utility values, and biological measures of disease activity.
Methods Symptoms of 608 patients on the United Kingdom Primary Sjögren's Syndrome Registry (UKPSSR) were reviewed.4 Phenotypes were identified using hierarchical cluster analysis of patient reported rating scales for pain, fatigue, dryness, anxiety and depression symptoms. Non-parametric analysis of variance was used to evaluate differences between clusters.
Results Four phenotypic clusters were identified: High symptom burden (HSB), Low symptom burden (LSB), dryness dominant (DD) and Low Anxiety and Depression (LAD). Not surprisingly, there were significant differences between these groups in measures of health status and quality of life (EQ-5D p<0.0001, TTO <0.0001). More interestingly, objective measures of disease activity (ESSDAI p=0.039), objective dryness (salivary flow p=0.007, Schirmer's p=0.014), and biological parameters (IgG p<0.0001, lymphocytes p=0.0005, ESR p=0.003) suggest these subgroups may reflect different underlying endotypes.
Conclusions Distinct biological differences may underlie pSS clinical phenotypes. The identification of these different clinical subsets of pSS could impact on the future study and management of the condition using a stratified approach.
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Acknowledgement We would like to thank all the patients and healthy volunteers who have participated in the UKPSSR. This study received grant support from the Medical Research Council, British Sjögren's Syndrome Association and the Newcastle University.
Disclosure of Interest None declared
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