CHEST Guidelines-Likely-False-Positive-Pneumococcal-Antigen-Test-Bi

Likely-False-Positive-Pneumococcal-Antigen-Test-Bi

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This document reports on a series of four cases where the pneumococcal antigen test BinaxNOW (PATB) produced false-positive results due to the presence of the anaerobic bacterium Parvimonas micra, rather than the suspected Streptococcus pneumoniae. This retrospective study from two hospitals involved patients with nonpneumococcal pleural empyema who had risk factors for aspiration pneumonia. In these cases, pleural fluid cultures were polymicrobial, with Parvimonas micra consistently present, and sequencing also identified Fusobacterium nucleatum. Importantly, further testing showed that the PATB cross-reacted with Parvimonas micra, leading to false-positive results, while specific tests for S. pneumoniae remained negative.<br /><br />Parvimonas micra, an anaerobic gram-positive bacterium part of the oral microflora, was identified as responsible for the cross-reactivity due to a common polysaccharide with Streptococcus species that the PATB detects. This discovery is notable, as such false positives have not been previously documented with this bacterium. Consequently, the authors stress the importance of cautious interpretation of PATB results, especially in the presence of anaerobic infections or co-infections in patients with aspiration pneumonia risk factors. The patients in this study included both children and adults with underlying conditions, all of whom recovered with appropriate antibiotic treatment.<br /><br />The authors emphasize that while the PATB is a valuable diagnostic tool, the potential for false positives necessitates careful case evaluation, particularly in anaerobic infections where polymicrobial cultures are likely. The study highlights the need for continuous evaluation of diagnostic tests to account for previously unrecognized cross-reactivities.

Keywords

Pneumococcal antigen test

BinaxNOW

false-positive results

Parvimonas micra

Streptococcus pneumoniae

pleural empyema

aspiration pneumonia

cross-reactivity

anaerobic infections

diagnostic evaluation