IISER Pune uses olfactory sense to help identify asymptomatic cases of Covid-19
Loss of sense of smell, a symptom of Coronavirus infection, can now be effectively and quickly measured by a novel method that has been developed by IISER, Pune researchers. Team led by Dr. Nixon Abraham from IISER’s Department of Biology, a custom built olfactory action meter was used to identify people with coronavirus infection showcasing no other typical symptoms. The researchers through this could detect olfactory deficits in almost 82% of people with asymptomatic Covid-19 infection. The method developed at IISER is 82% sensitive, 87% specific and 85% accurate.
The researchers tested 34 patients who were admitted to B J Government Medical College and Sassoon General Hospital in Pune. They were able to detect olfactory deficits in 82% of asymptomatic patients. The fact that only 15% of these asymptomatic people were aware of their loss of sense before the tests were performed, was the proof of highly effective test that is groundbreaking in detecting asymptomatic cases of Covid-19.
Experimental parameters were optimized by first testing normal healthy people using the new method. 37 healthy individuals were tested to assess their olfactory ability to detect 10 different odours at different concentrations of 9.1%, 16.6%, 23.1% and 50% v/v. The odours were exposed from lower to higher concentrations. Detection thresholds were based on detection ability of two consecutive odours. The detection abiltity was also noted for 50% v/v concentration. Lower of two concentrations was the detection threshold for an individual. All odours were delivered sequentially at set concentration level and then it was increased to next level. Sequence of odours was changed at each level. The test was participated by both healthy and asymptomatic individuals while wearing a mask.
It was found that majority of healthy participants could detect 8 out of the 10 odours at 16.6% v/v concentration, the second lowest concentration. The two remaining odours were detected at 23.1% v/v concentration. This identified the parameters for olfactory testing of Covid-19 patients. People have ‘olfactory deficit’ if they are unable to smell at all four concentrations, and ‘olfactory deficiency’ if they are unable to detect the odour at two or more out of the four concentrations.
Experiments found that 82% of the patient population (27 out of 33) and 13% of healthy participants (5 out of 37) had olfactory deficits. Dr. Abraham clarified, “Olfactory deficits can be seen even in healthy people and this can happen due to different reasons other coronavirus infection.”
Dr. Abraham is confident that the method can be used for mass screening for Covid-19 patients. He says, “Our work has laid the groundwork to use olfactory fitness as one of the prime criteria to identify people with asymptomatic infection. The methods and parameters established by our study can potentially be translated into a sensitive, fast and economical olfaction-based screening assay that can be self-administered by large populations.”