ABSTRACT
BACKGROUND: Rapid detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in hospitals is essential for early isolation and treatment. However, false positive test results can have adverse consequences for patient safety. CASE PRESENTATION: A man in his eighties was admitted to hospital with fatigue and new-onset gait and balance difficulties, without fever or symptoms of focal infection, but with elevated C-reactive protein. On admission, he tested positive on screening for SARS-CoV-2 using a fully automated rapid reverse transcription polymerase chain reaction (RT-PCR) test. He was placed together with two patients with confirmed COVID-19 infection in cohort isolation. Due to very low exposure risk and nonspecific symptoms, the primary and multiple subsequent test swabs were analysed using RT-PCR analyses guided by laboratory personnel, and all gave negative results. The patient had several risk factors for developing severe COVID-19 illness, but fortunately he remained COVID-19 negative on repeated tests. INTERPRETATION: The case presentation highlights the danger of false-positive SARS-CoV-2 test results, and the importance of interpreting a diagnostic test in the context of pretest probability and test accuracy. It also underlines the risk of using cohort isolation instead of individual isolation.