How is sjögren’s formally diagnosed?

Several ways. History, physical examination, lab tests for sjogren's antibodies and on occasion a "lip biopsy" removing some minor salivary glands from inside the lower lip to examine them microscopically.
Sjogren's syndrome. Sjogren's syndrome can be difficult to diagnose because the signs and symptoms vary from person to person and can be similar to those caused by other diseases. Side effects of some medications also mimic signs and symptoms of sjogren's syndrome. A variety of tests can help rule out other conditions and help pinpoint a diagnosis of sjogren's syndrome. Please see your doctor for evaluation.