Laboratory abnormalities include elevated ESR, ANA, anti-RF and hypergammaglobulinaemia. Do not rely on serological investigations for the identification of Sjögren's syndrome particularly with primarily neurological manifestations as these markers are negative and a significant proportion of cases.
Ophthalmological investigations for keratoconjunctivitis sicca can be helpful, as can biopsy of the salivary glands or an affected nerve in the case of peripheral neuropathy.