Nasal swab sampling for antigen test identifies COVID-19 well in all ages

ABSTRACT

Testing is essential for detecting COVID-19 and differentiating it from other respiratory infections with similar symptoms. We investigated the sampling depth to optimize the COVID-19 diagnostics in a real world decentralized setting. Subjects: 160 randomly selected subjects were included, all visiting medical center either exposed to COVID-19 or as symptomatic. Mean age was 17 years (range 1-79), and 57 subjects were <= 6 years of age. Method(s) Nasopharyngeal (NP) and anterior nasal (NS) specimen were collected from all and a subgroup of PCRor mid-turbinate (>=18 years) samples were included. All COVID-19 positive findings (NP or NS) were assumed to be true positives based on the high specificity of the used automated mariPOC (ArcDia Ltd, Finland) SARS-CoV-2 antigen test (>99.8%). Symptoms, COVID-19 vaccinations and other background information were obtained. Result(s) Detection of 11 possible different respiratory pathogens resulted in 41 NP-positive (26%) and 33 NSpositive (21%) results, of which positive for COVID-19 were 26 NP and 21 NS samples, respectively The best detection rate for COVID-19 was among subjects <=6 years of age, 100% for NS compared with 88% for NP. The negative percent agreement was high among all subjects regardless of symptoms (91-99%), whereas detection rate diminished by the length of sick days of >= 4. Conclusion(s) Anterior nasal specimen from the nostrils shows high potential in detecting COVID-19 in small children with a rapid antigen test. Nasal sampling may decrease the need of COVID-19 testing resources compared to NP swab, thus enabling allocation of resources for more effective infection control.