Introduction: Severe acute respiratory syndrome was first detected in 2003 and escalated in 2019 with COVID-19 causing a worldwide pandemic. This new virus presented challenges in diagnosis, especially in those under 6 years of age. While often classified as a mild disease in children, COVID-19 still presents significant health risks in the young, especially for children under 1 year of age and those with pre-existing comorbidities. Because of this, clinical guidelines and protocols addressing COVID-19 testing in preschool- aged children became necessary to direct evidence-based practice.

Aim: The aim of this systematic review was to explore COVID-19 testing and diagnosis in children under 6 years of age from international peer-reviewed published manuscripts to facilitate a wider and more thorough understanding of this practice from a diverse sample of parents, children, and health care providers to inform and direct practice within Aotearoa/New Zealand.

Methods: A systematic review was undertaken based on guidelines by Siddaway et al. (2019). Extant empirical research published in peer-reviewed journals from 2020–2024 on COVID-19 testing in children under 6 years of age was identified from Scopus, CINAHL, MEDLINE via PubMed, and PsycInfo via Ovid databases. Data were analysed using deductive thematic analysis.

Findings: Fourteen studies involving over 5,000 participants were included. Deductive content analysis identified seven key areas: 1. Symptomology, 2. Diagnostic tests, 4. Efficacy and acceptability of testing, 4. Viral loads, 5. Vulnerability/Risk factors, 6. Health outcomes, and 7. Recommendations.

Conclusion: While common symptoms such as fever and cough are prevalent in children under 6 years of age infected with COVID-19, symptomology alone is not a foolproof diagnostic tool. Additional diagnostic testing, such as nasopharyngeal swabs and polymerase chain reaction testing, is complementary to diagnosis. However, an understanding of the risk factors for contracting COVID-19, as well as the vulnerability and health outcomes of children with COVID-19, is important to consider.

Implications for practice: Common symptomology for children under 6 years of age includes fever and cough; however, these symptoms are also common for other viruses. A history of exposure to COVID-19 is the most frequent positive predictive factor for infection. An assessment of the child before any decisions on diagnostic testing is useful.