The stimulated salivary clearance of Tc-99m pertechnetate (SSCP) introduced in 1985 by Blue and Jackson is revisited here in patients with known or possible salivary disorders and correlated with most commonly cited and up-to-date quantitative indices obtained from standard dynamic salivary scintigraphy.
An SSCP test was performed after dynamic salivary scintigraphy in 19 patients with oral or ocular dryness, among whom 7 had Sjögren's syndrome. Many scintigraphic indices were calculated: salivary to background ratio (S/B[t]), background-corrected uptake U[t]), maximal uptake (Umax), cumulative gland uptake (CGU), initial slope of the uptake curve (IS), stimulated excretion velocity (SEV), stimulated excretion fraction (SEF), and excreted activity (EA).
The SSCP test was well tolerated, except in two patients in whom it had to be interrupted. Clearance values ranged from 5 to 40 ml/minute, with a clear-cut bimodal distribution centered around 15 to 20 ml/ minute. Six of the seven patients with Sjögren's syndrome had values less than 15 ml/minute. SSCP was closely correlated with all uptake indices (S/B, U, Umax, CGU, and IS) and uptake-related indices (EA, ISxSEF) (P < 0.01). A poor correlation was found with the excretion index SEV (P = 0.06) and none with SEF.
SSCP is a quick and objective means to investigate the sicca syndrome that may be useful in most clinical situations. It reflects the parenchymatous salivary gland function and will provide a means to assess and predict salivary gland involvement. Dynamic salivary scintigraphy remains necessary in very early stages because of its high sensitivity rate and ability to locate the impaired gland, or in severe stages in which lemon juice could be deleterious.