Real-time polymerase chain reaction (PCR), the gold standard for viral diagnostics in children, is a sensitive but resource-intensive method. Viral antigen tests are cheaper and more rapid but have lower sensitivity. The clinical relevance of PCR positivity has been questioned because of its high sensitivity and detection in asymptomatic individuals. Thus, we hypothesized that antigen test positivity might be more indicative of active infection than PCR positivity. The aim of this study was to evaluate the antigen test mariPOC Respi test for the detection of 10 respiratory viruses versus PCR in relation to viral load, days of illness, and immunological viral response.

Children 1–59 months old with lower respiratory infections were prospectively enrolled at the emergency department, Sachs′ Children and Youth Hospital, Stockholm, Sweden, between 2017 and 2019. Nasopharyngeal samples were collected from all cases (n = 314). The sensitivity and specificity of the mariPOC Respi test were assessed in children with and without an immunological viral response (defined as a blood myxovirus resistance Protein A level > 430 μg/L), using PCR as the reference standard.

The highest sensitivity for mariPOC Respi test was attained for respiratory syncytial virus (68%; 95% confidence interval: 63–73). Restricting the analysis to cases with a viral immunological response did not alter the results considerably.

These findings do not support the idea that mariPOC Respi test positivity to a higher degree than PCR correlates with clinical relevance, as indicated by an immunological viral response. The role of antigen tests in current clinical practice requires further discussion, particularly in the post–pandemic era.