P-1637. Limitations of Upper Respiratory Tract Testing in Diagnosing COVID-19 Pneumonia: A Retrospective Cohort Study

Abstract Background Upper respiratory tract (URT) testing including rapid antigen tests and RT-PCR of nasopharyngeal and oropharyngeal swabs has been the cornerstone for diagnosing SARS-CoV2 infection. However, emerging evidence suggests that negative URT results may not definitively exclude COVID-19 pneumonia, potentially delaying appropriate treatment. This study aims to evaluate the diagnostic yield of lower respiratory tract (LRT) testing and its implications for clinical severity.Concordance Between URT and LRT SARS-CoV-2 Testing ResultsTables showing the diagnostic concordance between upper respiratory tract (URT) and lower respiratory tract (LRT) SARS-CoV-2 tests in 511 patients. The first table includes all LRT-positive cases; the second applies a stricter LRT positivity definition with CT