Increasing the accuracy of the diagnosis of Sjögren's syndrome (SS) by placing emphasis on objective findings such as the presence of anti-Ro and anti-La autoantibodies and abnormal salivary gland tissue (SGT) histology is a current issue. In order to obtain optimal disease sensitivity and specificity of SGT findings, histological and immunohistological SGT examinations were compared. The first describes the extent of the lymphocytic infiltrate as a focus score (LFS), whereas the latter describes the composition of the infiltrate as a percentage of IgA-containing plasma cells (IgA%).
Both the LFS and IgA% score were assessed in 279 SGT biopsies taken from patients with symptoms suggestive of SS. In case histological conclusions did not match immunohistological conclusions patients were assigned to so-called mismatch groups. Patients in the mismatch groups were further classified using objective, serological parameters [rheumatoid factor (RF), anti-Ro, anti-La, anti-nuclear antibodies, gammaglobulin level].
In 249 samples (89%), LFS and IgA% resulted in the same conclusion. Within this group a total of 63 SGT samples (25%) were characteristic for SS showing LFS >1.0 and IgA% <70. In the mismatch groups after serological classification, both false positive as well as false negative scores were observed less frequently for IgA% as compared with LFS (50 vs 75% and 25 vs 50%, respectively).
Additional immunohistological SGT examination provides greater disease sensitivity and specificity than histological SGT examination alone, thereby increasing accuracy of SS diagnosis.