sicca syndrome doesn't mean necessary Sjogren Syndrome.how is seronegative ss diagnosed - and if it is just diagnosed with a Schirmer test, why would it be ss in the first place? That is a thinking that makes no sense in a way?
SS diagnosis needs either positive Salivary gland biopsy or positive antibodies to anti-SS-A and anti-SS-B antigens.
Seropositive SS means antibodies to anti-SS-A and anti-SS-B antigens.
Seronegative SS means no antibodies to anti-SS-A or anti-SS-B antigens (but positive salivary gland biopsy).
Diagnosis and Management of Sjogren Syndrome - American Family Physician (aafp.org)