2.4 Case Control Study
In the only study so far to institute validated quantitative olfactory testing Moein et al, in Iran, evaluated 60 patients who had tested positive for COVID-19. Their control group were selected from a group of 141 controls from a previously conducted study. They handpicked age and sex matched individuals from this cohort in an attempt to mirror their COVID-19 positive group. COVID-19 patients completed the Persian version of the 40-odorant University of Pennsylvania Smell Identification Test (UPSIT) assisted by a trained examiner, they do not explain how they administered the test in their previously investigated control group. Ninety-eight percent of their COVID-19 group had some level of OD with 25% of these subjects being completely anosmic. There was a statistically significant reduction in scores, in all 40 stimuli, within the COVID-19 group. There were no differences in demographics between the two groups but the way the control group was matched will have affected this data .