Portrait Toxigenic Clostridium difficile assay, an isothermal amplification assay detects toxigenic C. difficile in clinical stool specimens

Abstract

The Portrait Toxigenic Clostridium difficile assay is a rapid, qualitative assay for the detection of the tcdB gene of C. difficile in stool specimens from patients suspected of C. difficile infections, and received 510(k) clearance by the US FDA in March 2012. The Portrait Toxigenic C. difficile assay combines novel blocked-primer-mediated helicase-dependent multiplex amplification (bpHDA) technology and chip-based detection in an automated sample-to-result format. The assay requires minimal sample preparation and results are available within 90 min. In a multicenter evaluation, the Portrait Toxigenic C. difficile assay had a sensitivity of 98.2% and specificity of 92.8% compared with toxigenic culture. A comparative study between the Portrait Toxigenic C. difficile assay and three FDA-cleared molecular assays for the detection of toxigenic C. difficile exhibited a high degree of agreement (93.8–97.5%). The Portrait Toxigenic C. difficile assay provides a simple, cost-effective method with broad applicability to panel-based approaches, potentially simplifying workflow.

Keywords::

• Clostridium difficile
• C. difficile infections
• diagnostic test
• helicase-dependent amplification
• isothermal tcdB amplification
• nucleic acid amplification tests
• Portrait Toxigenic C. difficile assay
• sensitivity, specificity
• toxigenic culture

Financial & competing interests disclosure

The author has received honoraria and research funding from Great Basin Corp. and Becton Dickinson. The author has no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties

No writing assistance was utilized in the production of this manuscript.

Key issues

• The Portrait Clostridium difficile assay uses helicase-dependent amplification for DNA amplification which reduces instrument costs and increases reliability compared to PCR.

• The Portrait C. difficile assay incorporates blocked-primer-mediated helicase-dependent amplification which prevents the formation of primer artifacts during amplification, improving assay sensitivity and increasing the speed of amplification.

• The Portrait C. difficile assay combines multiplex isothermal amplification with chip based, spotted array visual detection which can provide more test parameters.

• The Portrait C. difficile assay is capable of detecting 10 CFU (95% probability of detection) of toxigenic strains of C difficile including NAP1/B1/027 directly in stool specimens.

• The Portrait C. difficile assay performance compared favorably with toxigenic culture and nucleic acid amplification tests. Timely reporting of results should have a positive impact on antibiotic therapy and infection control measures.

• The Portrait C. difficile assay performance did not appear to be influence by external parameters, such as geographic locations and study personnel.

• Optimization of testing for C. difficile infection should include diagnostic platforms for both detection of C. difficile and biomarkers of active infection.

• Physician education on test ordering habits and the use of molecular tests is important in interpreting C. difficile diagnostic assays.

Notes