In patients with sicca symptoms and positive SSA/SSB how often do you perform other diagnostic testing such as salivary gland ultrasound, biopsy, Shirmers, ocular staining, stimulated salivary flow, etc?

It depends on the clinical context, insurance coverage for procedures, availability of Sjogren's knowledgeable referrals, and patient preferences. I always have patients see optometry/ophthalmology in order to prevent ocular surface damage and assess the causes of dry eye (meibomian gland etc), and ...