The diagnosis value of beta 2-microglobulin and immunoglobulins in primary Sjögren's syndrome.

Salivary and serum concentrations of beta 2-microglobulin, salivary levels of the immunoglobulins, and salivary flow (as measured by a gravimetric method) were assessed in 34 patients and 11 controls. Of the 34 study patients, 16 had a primary form of Sjögren's syndrome (pSS) and 18 had sicca syndrome. The salivary and serum concentrations of beta 2-microglobulin and salivary levels of IgA and IgG were much higher in the patients with pSS than in controls or those with sicca syndrome (p < 0.001). Similarly, the salivary IgM levels of patients with pSS were higher (although at a lower degree of statistical significance) as compared to those of patients with sicca syndrome (p < 0.01) or controls (p < 0.05). No correlation was observed among the salivary flow and the salivary IgG and IgM levels, while there was a negative relationship (p < 0.01 with salivary IgA levels in all 45 patients considered as a whole. In 12 patients with pSS, the coefficient of correlation between the salivary gland biopsy focus score and the salivary (but not serum) concentration of beta 2-microglobulin was highly significant (p < 0.001). A similar relationship was observed with the IgG (p < 0.001) and IgM (p < 0.05) levels, but not IgA. In the diagnosis of pSS, the salivary IgA level demonstrates high sensitivity and low specificity. In contrast, serum and salivary concentrations of beta 2-microglobulin, salivary IgG, and to a lesser degree, salivary IgM have high specificity and positive predictive value.(ABSTRACT TRUNCATED AT 250 WORDS)