Characteristics of hyp- and anosmia in the context of Covid-19 infections

Introduction In the context of Covid-19, hyp- and anosmia are observed, which are different to the already known postviral olfactory dysfunction. With limited diagnostic test resources, the early detection of symptoms and their specificity for Covid-19 are of great importance, so that a better understanding of their characteristics is necessary. Material and methods As part of secondary prophylaxis, employees (n = 1734) from retirement and nursing homes were tested for SARS-CoV-2 and asked about subjective restrictions on the sense of smell and any nasal co-symptoms. In addition, patients (n = 41) after confirmed and healed Covid-19 infection were questioned and examined with regard to hyp-/anosmia using a questionnaire and olfactory testing (Sniffin 'sticks with SDI rating). Results Approx. 1% of the employees surveyed reported subjective hyposmia. Acute hyposmias were accompanied by nasal obstruction, chronic hyposmias showed no co-symptoms. In the patients after Covid-19 infections, the identification (Imed = 14) and the discrimination (Dmed = 12) of the odors were only slightly limited, but there was a persistent pathologically increased threshold value for odor perception (Smed = 1.75) in the median 75 days after the onset of infection. Discussion Acute hyp-/anosmia without nasal co-symptoms rarely occurs in the SARS-CoV-2 negative population, so that its occurrence is currently suspicious of a Covid-19 infection and should be examined further e.g. via nasopharyngeal swab. In the further course the odor restrictions can regress again, the different odor qualities seem to do this with different latencies, whereby the increased odor threshold persists the longest.