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 .