Quantitative immunohistologic study of lip biopsies. Evaluation of diagnostic and prognostic value in Sjögren's syndrome.

In a group of 45 patients with Sjögren's syndrome (SS) and 80 controls the high specificity (95%) and sensitivity (100%) of a recently proposed bivariate quantitative immunohistologic (QIH) criterion for SS, based on percentages of IgA and IgG-containing plasma cells in labial salivary gland (LSG) tissue, was confirmed. The best univariate QIH criterion for discrimination between LSG biopsies of SS patients and controls appeared to be based on the percentage of IgA containing plasma cells, and had a specificity of 99% and a sensitivity of 96%. A criterion based only on the percentages of IgM-containing plasma cells, proposed in another recent study, resulted in a high number (31%) of false negatives. Interobserver reproducibility of QIH diagnoses was excellent. Moreover it was demonstrated that accuracy, precision and the interobserver reproducibility of plasma cell counting depends on the choice of tissue fixation and immunohistologic staining procedure. The combination of formol sublimate fixation and peroxidase anti-peroxidase procedure appeared to be the best combination for QIH examination. Furthermore, in 2 SS patients systemic monoclonal IgM/kappa gammopathy was preceded by high predominance of IgM and kappa containing plasma cells in the plasma cellular infiltrate of the LSG tissue.