Subtle olfactory dysfunction after SARS-CoV-2 virus infection in children

Objectives: Anosmia/hyposomia have been described as early signs of COVID-19 infection in adults, including young asymptomatic patients who commonly refer olfactory disfunction as their only clinical manifestation. Very few studies involving paediatric age patients have been published until now. This study aims to determine the presence of olfactory dysfunction in children with COVID-19 infection through the use of a self-reported questionnaire and a new olfactory screening tool. Methods: Nested case-control study. All paediatric patients screened by reverse transcription polymerase chain reaction (RT-PCR) and Anti-SARS-CoV-2 antibodies for COVID-19 infection, during the study period (March-May 2020), were asked to respond to a questionnaire about symptoms of olfactory disfunction. Patients above six years old also performed an odor identification test based on seven odorants (Kradeo (R)). This test was designed based on our cultural context and eating habits. Results: 126 patients were recruited, including 33 with COVID-19 infection. 15% of the infected children referred anosmia and/or dysgeusia on the questionnaire, all of them were older than eleven years. The results of the odor test (69 patients) revealed subtle disturbances in the infected group (mostly misrecognition of odorants). Median odorant recognition was 3 odors [Interquartile range (IQR) 2-4] in case group and 4 [IQR 3-5] in controls. Male patients showed significantly larger disturbances than girls in both groups (p = 0.03). Conclusion: Self-referred prevalence of olfactory disfunction in our sample of infected children is lower than that described in adults, especially among the youngest ones, maybe due to immature development of angiotensin-converting enzyme 2 (ACE2) receptors expressed in nasal mucosa. Nevertheless, one month after infection, subtle disturbances (misrecognition of odors) were identified among the infected children. This screening olfactory test provides a hygienic, user-friendly tool, suitable for screening children older than six years of age.