Misdiagnosis Due to False-Positive Detection of Pneumococcal Urinary Antigen

Notomi, Kaori and Harada, Taku and Watari, Takashi and Hiroshige, Juichi and Shimizu, Taro (2022) Misdiagnosis Due to False-Positive Detection of Pneumococcal Urinary Antigen. European Journal of Case Reports in Internal Medicine, 9 (2). pp. 1-3. ISSN 2284-2594

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Introduction: The detection of pneumococcal antigens in urine is an alternative to gram staining, and their culture is central to the diagnosis of pneumococcal pneumonia. We present a case of the false-positive detection of urinary Streptococcus species pneumococcal antigen with a BinaxNOW test. This resulted in delayed diagnosis of a liver abscess. Case description: A 70-year-old woman presented to the emergency department with a 1-day history of chills and difficulty walking. She had a fever and her physical examination was normal. Non-contrast chest computed tomography (CT) revealed a slight ground-glass opacity in the left lower lobe. Laboratory tests revealed liver injury and elevated C-reactive protein levels. A urinary pneumococcal antigen test was positive, and she was diagnosed with acute bronchopneumonia caused by Streptococcus pneumoniae. She was treated with ceftriaxone. However, abdominal contrast-enhanced CT performed the next day revealed portal vein thrombus and a left lobe liver abscess. Streptococcus constellatus was detected in a puncture specimen of the liver abscess. It was concluded that the positive urinary pneumococcal antigen test was a false-positive owing to Streptococcus infection. Discussion: False-positive results might be explained by the presence of C-polysaccharide antigens in the cell wall of S. pneumoniae. The positive urinary antigen test together with the finding of slight ground-glass opacity in the left lung on chest CT initially led to misdiagnosis. False positives may result in misdiagnosis and unnecessary antimicrobial therapy.Conclusion: The overuse of the pneumococcal urinary antigen tests can lead to false positives and misdiagnosis.

Item Type: Article
Uncontrolled Keywords: Pneumococcal urinary antigen, pneumococcal pneumonia, Streptococcus, liver abscess, false-positive, misdiagnosis
Subjects: 600 Tecnologia - Scienze applicate > 610 Medicina e salute (Classificare qui la tecnologia dei servizi medici)
Depositing User: Marina Spanti
Date Deposited: 14 Apr 2022 12:35
Last Modified: 14 Apr 2022 12:35
URI: http://eprints.bice.rm.cnr.it/id/eprint/21799

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