Evaluation of the performance of direct nasopharyngeal swabs for Acute Respiratory Syndrome molecular diagnostics by the highly multiplex STAT-Dx Respiratory System

Background:

Respiratory infections are a frequent reason for seeking medical care. Rapid identification of the causative pathogen is important to optimize care and minimize unnecessary use of antibiotics. Multiplex PCR tests are rapidly becoming the preferred approach for obtaining an actionable diagnosis. These highly sensitive methods allow usage of low-invasive sampling techniques such as oropharyngeal (OPS) and nasopharyngeal swabs (NPS). NPS have been shown to yield high viral loads across age and clinical settings. They avoid the risk of aerosol transmission that can theoretically occur with nasopharyngeal aspirates if the suction device is not connected to a water lock or a filter. Direct insertion of the swab in the assay device would further increase patient and healthcare worker safety by minimizing transmission risk from potential spills or aerosol as well as errors when handling or transferring the swab transport medium (UTM).

Materials/methods:

The DiagCORE® Respiratory Panel assay (DC-RP) is a closed cartridge-based multiplex molecular test assay that combines nucleic acid (NA) extraction from clinical specimens, multiplex real-time PCR, and post-PCR analysis. It is operated on the highly automated DiagCORE® analyzer for an assay turn-around time of about 1 hour. It tests for the presence or absence of 17 viral and 3 bacterial NA of respiratory pathogens.The cartridge can test both liquid and direct (´dry´) swab samples, trough dedicated sample ports.

Testing was performed both at the manufacturer and in the clinical microbiology lab of the university of Bonn, a tertiary 1200 bed teaching hospital. Swabs dipped in positive UTM obtained from patients with a respiratory syndrome as well as OPS and NPS directly obtained from such patients were pairwise compared to UTM samples.

Results:

All groups of DC-RP pathogens were represented in the study. Direct swab samples (189) showed a sensitivity of 98,4% (95% CI: 95,1% -99,6%) compared to UTM samples, while a higher yield for several targets was observed in the NPS, as evidenced by better CT values.

Conclusions:

Testing of direct swabs in the DC-RP cartridge was found to be highly accurate. This unique ability will support safe testing practices in both the laboratory and the point-of-care setting.

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