Validation of a new scale to assess olfactory dysfunction in patients with Parkinson´s Disease

Abstract

Bakckground: Olfactory dysfunction is present in up to 90% of Parkinson's disease (PD) patients. It is usually evaluated by means of objective standardized tests; however no self-administered scales have been developed for olfactory dysfunction bedside assessment. We present validation of a new scale to assess this symptom in PD patients. Methods: Seventy-five PD patients and 25 control subjects were evaluated using a Hyposmia Rating Scale developed in-house, combined with the extended Sniffin' Sticks test. Results: Total score of the 6-item Hyposmia Rating Scale showed significant correlation with threshold, discrimination, identification and total Sniffin' Sticks test scores (r = 0.53; r = 0.60; r = 0.57; r = 0.65 respectively, p < 0.001 for all values). Area under the curve of the receiver operating curve for the ability of Hyposmia Rating Scale to discriminate patients with Sniffin' Sticks test total scores below or above the cut-off point was 80 ± 6% (p < 0.001). Considering Sniffin' Sticks test as the gold standard method for olfactory dysfunction detection, an affirmative response to a single screening question about smelling ability problems showed 35% sensitivity (95%CI = 23-47%) and 100% specificity. The best cut-off point for Hyposmia Rating Scale was 22.5 with a sensitivity of 70% (60-81%) and a specificity of 85% (65-100%). Conclusion: The Hyposmia Rating Scale here presented may offer a simple, cost-effective, time-saving and reliable approach to evaluate olfactory dysfunction in PD patients.