Discrepancy between subjective symptoms, objective measures and disease activity indexes: the lesson of primary Sjögren's syndrome

Mucosal dryness is a key clinical feature in primary Sjögren's syndrome (pSS) and its assessment relies on both objective measurement of residual secretion and subjective symptoms reported by patients. However, while the objective assessment and grading of glandular dysfunction can be easily performed, the spectrum of clinical symptoms encompassed by the terms 'dry eye' and 'dry mouth' is wide and heterogeneous. Therefore, patient reported outcomes (PROs) for dryness in pSS poorly correlate with the amount of glandular secretion. In addition, subjective dryness is not correlated with the severity of systemic disease and severely affects the patient quality of life even in presence of active extraglandular manifestations. The purpose of this review article is to provide an overview of glandular dysfunction in pSS as well as the impact of discrepancy between objective assessment, subjective symptom and extraglandular disease activity on disease management.