Evaluation of MST for Unstimulated Salivary Flow Assessment

The sensation of dry mouth may be an early symptom of several morbid conditions that require immediate attention. Even though several methods are available for the evaluation of salivary gland hypofunction, these are rarely used in general private practice. Objective: To evaluate the modified Schirmer tear-test strip method (MST) for measurement of unstimulated whole salivary flow rate [cut-points used:  0.1 ml/min and  0.2 ml/min], by comparing it with the most widely used salivary flow rate draining test in a clinical study. Methods: Using a screening survey and a review of the medical history, 66 patients who had agreed to participate in this IRB approved study and signed a consent form were divided into two groups: (A) healthy patients and (B) patients at risk of hyposalivation. Every patient was then tested for salivary flow rate using the MST and the draining method (the order of which were randomized). The patient's caries experience (DMFT) was also measured. In addition, ten patients from each group were retested on a different day to obtain reproducibility data. Viscosity was measured from every sample collected from which there was enough saliva, by measuring the contact angle. Results: MST with a cut off value of ≤10mm/3min readily distinguished the unstimulated whole saliva flow between healthy asymptomatic subjects and subjects who experienced profound xerostomia and hyposalivation (sensitivity 73%; specificity 91%). Reproducibility of the draining saliva flow rate and MST measurements was excellent (ICC of 0.90 and 0.96 respectively). The viscosity of the unstimulated saliva was weakly correlated (r=0.25) with the MST. There was a strong positive association (r=0.80) between DMFT and viscosity for the subjects with hyposalivation. Conclusion: The MST method with a cut offs value of £10 mm/3min could be used as an easy alternative for whole unstimulated salivary assessment.