Introduction and objective: Respiratory syncytial virus is a major cause of lower respiratory tract infections, particularly in children under two years of age. Diagnostic methods include rapid antigen diagnostic tests, which have shown high specificity and variable sensitivity. The aims of this study were to verify the performance of these tests in hospitalised children, and to identify factors influencing the results. Materials and methods: The study enrolled children under two years old who were tested for respiratory syncytial virus using both rapid antigen diagnostic test and a cartridge-based nucleic acid amplification test. The sensitivity, specificity, and positive and negative predictive values of the tests were calculated. The influence of symptoms and fever duration, socioeconomic conditions, presence of siblings, and feeding method were analysed. Results: A total of 164 patients aged 10 days to 24 months (median 2.5 months) were included. Sensitivity reached 75% (95% confidence interval: 67.3–81.7%), specificity – 100% (73.5–100%), positive predictive value – 100%, and negative predictive value – 24% (19.3–29.4%). Lower sensitivity was associated with longer duration of signs/symptoms, with the lowest value obtained in the group with 6–7 days of signs/symptoms – 47.4% (24.5–71.1%), which differed from the 2–3 days group (p = 0.005) and the 4–5 days group (p = 0.016). No association was found between sensitivity and patient age, socioeconomic conditions, presence of siblings, clinical course including fever, or feeding method. None of these factors affected specificity, positive or negative predictive value. Conclusions: The reliability of the rapid antigen diagnostic tests in cases of positive results appears to be high, though negative results should be interpreted with caution. Prolonged duration of signs/symptoms before testing might reduce the level of sensitivity.

children, sensitivity, specificity, respiratory syncytial virus, rapid antigen diagnostic test