Morphometry in the diagnosis of Sjögren's syndrome.

Sublabial salivary gland biopsies of 20 patients with Sjögren's syndrome and 58 controls were analyzed morphometrically to determine which histologic changes in the tissue are specific enough to justify a diagnosis of Sjögren's syndrome and which changes are due to physiologic aging. The acinar atrophy, fibrosis, ductal hyperplasia and ductal dilatation mentioned in the literature as features of Sjögren's syndrome are also observed in the tissue of aging individuals, and the lymphocytic focus score cited as the most important diagnostic parameter gives rise to about 9% of false-positive diagnoses. When using single quantitative histologic parameters, the volume percentages (Vol%) of lymphocytic foci, diffuse lymphoplasmacytic infiltrate (DLPI), acini and the inner diameter of intralobular ducts (ILD) were able to discern between the patients and the controls at a significant level, regardless of age, although considerable overlap was still present. This overlap could be reduced by consideration of at least two histologic parameters. The inhomogeneity within the tissue constituents was also used in discriminating between the patients and the control subjects. The best bivariate discriminating combination of histologic parameters was Vol% of lymphocytic foci and DLPI. Compared with qualitative subjective evaluation, this morphometric decision rule in the present material gave a 5 X reduction in the number of false-positive diagnoses of Sjögren's syndrome, with only 1 of the 58 control subjects erroneously classified as having the syndrome. We conclude that quantitative investigation of sublabial salivary gland tissue will improve the diagnostic criteria needed for the definition of Sjögren's syndrome.