Subjective Smell Disturbances in Children with Sars-Cov-2 or Other Viral Infections do not Correspond with Olfactory Test Results

Background Olfactory dysfunction associated with SARS-CoV-2 infection in children has not been verified by a validated olfactory test. We aimed to determine whether these complaints are objectifiable (test-based hyposmia), how often they occur during acute SARS-CoV-2 infection compared to other upper respiratory tract infections (URTI), as well as in children recovered from COVID-19 compared to children with long COVID.Methods Olfactory testing (U-sniff test; hyposmia<8 points) and survey-based symptom assessments were performed in 434 children (5-17 years; 04/2021-06/2022). 186 symptom-free children served as controls. Of the children with symptoms of acute respiratory tract infection, SARS-CoV-2 PCR test results were positive in 45 and negative in 107 children (URTI group). Additionally, 96 children were recruited at least 4 weeks (17.6 +/- 15.2 weeks) after COVID-19, of whom 66 had recovered and 30 had developed long COVID.Results Compared to controls (2.7%), hyposmia frequency was increased in all other groups (11-17%, p<0.05), but no between-group differences were observed. Only 3/41 children with hyposmia reported complaints, whereas 13/16 children with complaints were normosmic, with the largest proportion being in the long-COVID group (23%, p<0.05).Conclusion Questionnaires are unsuitable for assessing hyposmia frequency in children. Olfactory complaints and hyposmia are not specific for SARS-CoV-2 infection. The number of complaints in the long-COVID group could result from aversive olfactory perception, which is undetectable with the U-sniff test.