Measurement of whole unstimulated salivary flow in the diagnosis of Sjögren's syndrome.

The criteria for a clinical diagnosis of Sjögren's syndrome remain controversial and vary widely from study to study. With respect to the oral component it is considered necessary to use some form of objective test, but many of those available are not suitable for use in a busy clinical situation. The purpose of this study was to evaluate a simple method for measuring the whole unstimulated salivary flow. Twenty five patients with Sjögren's syndrome, 69 young control subjects, 20 age matched normal older control subjects and 20 patients with rheumatoid arthritis without Sjögren's syndrome had their salivary flows measured. Whole unstimulated salivary flows in the young control subjects were higher than in all other groups. Patients with primary Sjögren's syndrome had lower flows than either the older controls or the rheumatoid patients. Among the patients with Sjögren's syndrome 52% had a flow of 0.1 ml/min or less compared with only 8% of age matched controls. The positive predictive value of this low flow was 81%. It is concluded that whole unstimulated salivary flows of 0.1 ml/min or less are highly specific for xerostomia. When interpreted in the context of all the clinical findings whole unstimulated salivary flows are useful for diagnosing the oral component of Sjögren's syndrome.