1004. Performance evaluation of the cobas® Strep A assay for point-of-care diagnosis of streptococcal pharyngitis in CLIA-waived primary care settings
Session: Poster Abstract Session: Diagnostic Microbiology: Streptococci
Friday, October 9, 2015
Room: Poster Hall
Posters
  • IDSA2015StrepAFINAL.pdf (383.1 kB)
  • Background: Group A streptococci are a leading cause of pharyngitis. CLIA-waived rapid antigen-based tests are commonly performed by non-laboratory trained staff in primary and urgent care settings to help diagnose pharyngitis at the point-of-care, but they can demonstrate low sensitivity. The cobas® Strep A assay is an easy-to-use, CLIA-waived PCR test on the cobas® Liat System for detection of Streptococcus pyogenes from throat swabs. We determined the performance of the assay in CLIA-waived settings using operators with no laboratory training.

    Methods: The cobas® Strep A assay was evaluated at 5 CLIA-waived sites by 17 non-laboratory trained staff. Throat swabs were prospectively collected from patients with signs and symptoms of pharyngitis. For comparison, the site’s standard-of-care diagnostic methods (i.e. rapid antigen-based test, and/or diagnostic culture) were also performed. Results were compared to reference microbiological culture. 

    Results: On 427 throat swabs, the cobas® Strep A assay demonstrated 97.7% sensitivity and 93.3% specificity compared to reference microbiological culture. Discordance analysis using PCR and bi-directional sequencing confirmed the positive cobas® Strep A result for all PCR positive, culture negative specimens. In comparison, the rapid antigen-based test on 427 specimens demonstrated 84.5% sensitivity and 95.3% specificity compared to reference culture. Similarly, site diagnostic culture on 310 specimens demonstrated 86.8% sensitivity and 97.0% specificity compared to reference culture.

    Conclusion: The cobas® Strep A assay on the cobas® Liat System automates and integrates sample purification, nucleic acid amplification, and detection of Streptococcus pyogenes with a sample-to-result time of about 15 minutes. No reagent preparation, sample manipulation, or other operator intervention is required. The high accuracy, rapid time to result and remarkable ease of use make the cobas® Strep A assay for use on the cobas® Liat System a highly suitable point-of-care solution for the diagnosis of group A streptococci infection.

    Fangnian Wang, MD, PhD1, Yu Tian, PhD1, Ying Valcour, MS1, Thomas Drechsler, BS1, Robert Luo, MD, MPH2 and Lingjun Chen, BA1, (1)Roche Molecular Systems, Marlborough, MA, (2)Roche Molecular Systems, Pleasanton, CA

    Disclosures:

    F. Wang, Roche Molecular Systems: Employee , Salary

    Y. Tian, Roche Molecular Systems: Employee , Salary

    Y. Valcour, Roche Molecular Systems: Employee , Salary

    T. Drechsler, Roche Molecular Systems: Employee , Salary

    R. Luo, Roche Molecular Systems: Employee , Salary

    L. Chen, Roche Molecular Systems: Employee , Salary

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