Rheumatology is really a mess right now. Doctors thought they could divide up the more common rheumatological diseases by the ENA, or extractable nuclear antigens. As it turns out, the specific ENA's are not that helpful for many people with a positive ANA. A fairly large percentage or people, with high ANA's, >1:640, still are negative when it comes to ENAs....so, yes, they have a connective tissue disease or autoimmune disease, but the type can only be assigned by symptoms.
I am in the same boat, a high >1:1280 ANA, but negative ENA, with +lip biopsy. All the other tests they do for SjS, were + for SjS....such as Schirmers etc. Am I convinced I have SjS? No. I don't think that Rheumatology has defined the criteria to make a spit of sense as of yet.
Sicca is just one constellation of symptoms of SjS. If your ANA is substantially high, you have an autoimmune condition. With a + lip biopsy, you can be classified as having SjS, which is an autoimmune disease. Sicca is dry eyes and dry mouth, regardless of etiology. Sicca may have nothing to do with autoimmune disease.