Olfactory Function Assessment: Standardization of a New Quantitative Technique for the Indian Population

Aim: Olfactory function assessment is often neglected in clinical settings due to a lack of appropriate cost effective techniques. We therefore aimed to develop a cost effective, reliable and culturally appropriate tool for olfactory function assessment among the Indian population and to compare olfactory functions among 63 healthy controls and 32 idiopathic Parkinson’s disease patients.

Materials and Methods: Olfactory stimuli were applied to the nostrils of the participants using an olfactometer. Five different odoriferous substances common to Indian culture were used for the study in three different concentrations: ginger (1%, 2%, 3%), cardamom (0.4%, 2%, 3%), garlic (0.8%, 1.4%, 2%), coffee (1.6%, 2%, 4%), vanilla (2%, 3%, 4%). Olfactory recognition threshold, olfactory identification score and olfactory discrimination score were observed among the control population and Parkinson’s disease population.

Results: The olfactory recognition threshold was significantly high among the Parkinson’s disease group compared to controls (Mann Whitney U test, p<0.001). Reliability was tested using the test-retest method among the control group and all olfactory variables in three different concentrations had either r value closer to 1 or 1, which shows an acceptable level of reliability. The correlation was found to be significant (p<0.001). A receiver operating characteristic (ROC) curve drawn for olfactory recognition thresholds at different concentrations for the five odouriferous substances and the area was determined to classify cases and controls (Determined areas: ginger = 0.928, cardamom = 0.955, garlic = 0.921, Coffee = 0.950, vanilla = 0.950). The area under the curve was found to be significant in classifying the cases and the control.

Conclusion: The newly developed olfactory assessment tool was found to be reliable and effective in assessing olfactory parameters like recognition threshold, identification score and discrimination score among the Indian population.