Diagnostic accuracy of salivary scintigraphic indices in xerostomic populations

Purpose: Three decades of work to enhance the diagnostic accuracy of saliva ry scintigraphy have generated various plausible decision criteria. This st udy evaluates four commonly cited numeric indices in studies of xerostomic populations and how accurately they identify Sjogren's syndrome, chronic si aladenitis, radiation sialadenitis, and drug effects and distinguish each f rom the other. Methods: Stimulated dynamic salivary scintigraphy was performed on 295 xero stomic patients and on 31 controls. The nonparametric area under the receiv er operating characteristic curves expressed the diagnostic accuracy of the following scintigraphic indices: the parotid:submandibular ratio of unstim ulated glandular activity, the peak:baseline uptake ratio, its time of occu rrence, and the stimulated excretion fraction. Results: The stimulated excretion fraction distinguished Sjogren's syndrome and radiation sialadenitis from healthy states with respective accuracies of 0.78 and 0.90. The maximum diagnostic payoff in Sjogren's syndrome occur red at a cutoff of 73%, yielding a 73% rate of test sensitivity and a 73% r ate of specificity. The other three indices were not useful. Even the stimu lated excretion fraction performed indifferently or poorly in most other di agnostic tasks. Conclusions: In the scintigraphic examination of xerostomic and healthy pop ulations, an acceptable diagnostic utility of the stimulated excretion frac tion was evident only in Sjogren's syndrome and radiation sialadenitis. Whe n presented with differential diagnostic alternatives not involving radiati on sialadenitis, none of the four numeric indices performed acceptably.