Salivary gland scintigraphy in Sjögren's syndrome: are quantitative indices the answer?

We evaluated the role of quantitative indices derived from dynamic 99mTc-pertechnetate salivary scintigraphy in the differentiation between a group of patients with Sjögren's syndrome (SS), a group of patients without xerostomia, but with underlying autoimmune disorders, and a group of controls. Seventeen patients with SS (group A), 18 patients with autoimmune disorders (group B) and 15 controls (group C) underwent dynamic salivary gland scintigraphy. Functional indices for the parotid and submandibular glands were calculated and comparisons were made between the groups. There were no significant differences between the three groups in terms of the maximum accumulation (MA), maximum secretion (MS) and pre-stimulatory oral index (PRI). The uptake ratios (URs) for both the right and left parotid glands and the left submandibular gland in group A were significantly lower than those in group C, but no different from those in group B. The URs for the parotid glands in group B were significantly less than those in group C. The percentage uptake by the right parotid gland at 4 min (U4) was significantly lower in group A than in groups B or C, and lower than the percentage uptake by the left parotid gland at 4 min in group A. The rest of the U4 values and all of the uptakes at 14 min (U14) were not significantly different between the three groups. The time taken for the right parotid gland to reach peak activity (Tmax) was significantly less in group A than in the other groups, but other glands showed no significant differences. It can be concluded that MA, MS and PRI cannot be used to differentiate between the three groups. The URs in groups A and B were no different, but were significantly lower than those in group C. However, the extensive overlap between xerostomic patients and normal controls for all the quantitative indices calculated imposes a severe limitation on their discriminatory power.