Salivary immunoglobulins in the diagnosis of primary Sjögren's syndrome

The salivary concentrations of immunoglobulins and total proteins and the salivary flow rate (measured by the method of Deniker et al.) were determined in 29 patients with keratoconjunctivitis sicca and xerostomia and in 11 healthy subjects. According to Fox criteria the group pf 29 patients was divided into two groups: 14 patients with primary Sjögren's syndrome (pSS) and 15 patients with sicca syndrome (SS). The IgA salivary levels were significantly higher in the patients with pSS than in the patients with SS (p < 0.05) and in the healthy subjects (p < 0.001). Moreover the IgG and IgM salivary levels in the first group of patients were higher than in the group of patients suffering from sicca syndrome (p < 0.05) and in the control group (p < 0.02). The salivary flow rate of the patients with pSS and sicca syndrome was lower when compared with the control group (p < 0.005). No significant correlation was found between the salivary flow rate and the immunoglobulins in the three groups of patients. The salivary flow was inversely correlated (p < 0.01) only with the IgA levels in all 40 subjects. The salivary total proteins were significantly elevated in pSS patients when compared with the SS patients (p < 0.04) and with the control group (p < 0.01). The immunoglobulins/total proteins ratios in saliva were significantly higher in the first group than in the other groups (p < 0.005) for the IgG and in the first group than in the SS patients (p < 0.05) for the IgM; no significant differences were noted for the IgA. The bioptic focus scores, graded according Greenspan's criteria, of minor salivary glands of 20 patients with pSS or sicca syndrome were directly correlated with a high significance (p < 0.001) to IgG salivary levels and with a lower significance (p < 0.05) with IgM salivary levels. No significant correlation was found between the bioptic focus scores and the IgA levels. The present results demonstrated a high specificity (100%) and a good sensitivity (86%) of the assessment of salivary IgG for the diagnosis of pSS. The sensitivity of the salivary levels of IgA was higher than that of IgG (93%) but the specificity was low (50%); on the contrary the specificity of the assessment of salivary IgM was good (92%) but the sensitivity was low (60%). This study therefore indicated that the assessment of salivary IgG has a great value for the diagnosis of pSS because IgG levels are related to the amount of lymphoplasmocytic infiltration.