Use of Indian smell identification test for evaluating olfaction in idiopathic Parkinson's disease patients in India

Background: Olfactory dysfunction in Parkinson's Disease (PD) has been recognized for a long time and a number of studies have been performed in various parts of the world, using culturally appropriate smell identification tests. Objective: In this study, for the first time, olfactory function has been assessed in the Indian Idiopathic Parkinson's Disease (IPD) patients using an indigenously developed smell test. Materials and Methods: Olfaction was assessed in 53 IPD patients and 50 healthy controls using SniffIn-sticks (R) test and Indian Smell Identification test (INSIT). In both these tests, the subjects were asked to identify the smell from a set of choices and were scored out of 10 and 12 for INSIT and SniffIn-sticks (R) test, respectively. Results: Both SniffIn-sticks (R) test and INSIT showed significant impairment in olfaction in IPD patients (P < 0.001). There was no significant correlation of the scores of both tests with Hoehn and Yahr (H and Y) stage, duration of illness and Levodopa Equivalent Daily Dose (LEDD). The tests had a high correlation, r = 0.75 (P < 0.001) and the area under the Receiver Operating Characteristic (ROC) curves did not differ significantly. Using a cut off value of 4 (values <= 4 indicating disease), INSIT showed a sensitivity of 79.2% and specificity of 78%. Conclusion: INSIT, being cheap, convenient and more acceptable in the Indian population, can be considered as a better alternative for SniffIn-sticks (R) test in the evaluation of olfaction in Indian PD subjects.