Prompt diagnosis of invasive fungal diseases and administration of antifungal treatment is crucial to infected patients’ survival, but current diagnostic techniques are suboptimal, with low sensitivity and time-consuming, labour-intensive processes. Practical Patient Care speaks to Alastair McInroy at Renishaw Diagnostics about how the company is working to achieve precise and timely diagnoses, and avoid patients’ overexposure to unnecessary preventative medicines.
What are the major challenges of detecting and treating invasive fungal disease (IFD)?
Alastair McInroy: IFD is life-threatening in patients receiving immunosuppressive therapies, such as those prescribed for solid organ transplants and haematopoietic stem cell transplants, and in patients suffering immune-compromising conditions such as AIDS. Many institutions adopt a preventative approach to patient management, where at-risk patients are administered antifungal therapies without a confirmed diagnosis. Given the relatively low prevalence of disease, this has led to the exposure of a large population of patients to unnecessary – and potentially toxic – antifungal agents, while increasing pharmaceutical costs to the healthcare provider.
Diagnosis of IFD must therefore be improved to allow a targeted approach to patient management, in which only those diagnosed with fungal disease receive the appropriate therapies.
How did the Multiplex Assay System and the Fungiplex assay come into development?
The RenDx Multiplex Assay System is a PCR-based diagnostic platform that enables the identification of target DNA associated with particular pathogenic organisms.
The system uses detection technology known as surface-enhanced resonance Raman scattering (SERRS). The technology and company were spun out of the University of Strathclyde (Glasgow) in 2007, before becoming part of the Renishaw Group, a world leader in engineering and industrial metrology. Renishaw Diagnostics represents the Group’s expansion into healthcare and its application of precision engineering to new markets. The system’s first assay, Fungiplex, allows the detection of 12 Candida and Aspergillus species: the most prevalent causative agents of IFD.
How does the use of SERRS make the RenDx system unique, and what benefits does it have over other techniques?
While most PCR-based diagnostic systems operate using traditional fluorescence detection, the RenDx system uses SERRS. This highly sensitive, information-rich technique produces a detailed vibrational spectrum or ‘fingerprint’ for each target analyte within a sample. Each ‘fingerprint’ can be easily discerned from others within a particular sample, allowing significant improvement on the levels of multiplexing achievable from traditional methods. In addition, SERRS has been shown to be far more sensitive than fluorescence, making it ideal for applications where ultimate sensitivity is crucial, such as in diagnosis of IFD.
And what direct benefits does the RenDx system offer patients?
Because the RenDx Fungiplex assay has the potential to aid earlier diagnosis of IFD, patient outcomes could be improved, hospital stays reduced and the use of oft-unnecessary antifungal therapies minimised. The introduction of molecular methods, in addition to traditional methods such as culture and radiological screening, creates a suite of tests that can greatly improve diagnosis of disease.
In particular, PCR has been shown to significantly improve early diagnosis when used alongside additional molecular techniques such as galactomannan antigen detection. However, current PCR assays in this area have been limited in scope, due to the restrictions in multiplexing imposed by their underlying detection technologies. The RenDx Fungiplex assay provides a broad information set on the two most common causative agents of IFD, and highlights the species resistant to first-line treatment therapies. With the high sensitivity afforded by the underlying technology, the RenDx Fungiplex assay is a powerful tool in the move towards the diagnostics-driven treatment of IFD.
What developments are in the pipeline for the RenDx system?
Renishaw Diagnostics is currently focused on demonstrating the clinical utility of the Fungiplex assay when used alongside additional fungal diagnostic techniques in relevant patient populations. Following on from this, we hope that the Fungiplex assay will form part of the argument to move from prophylaxis to a diagnostics-driven approach to antifungal stewardship.
In addition to Fungiplex, Renishaw Diagnostics is developing two further assays due for launch in 2016: Gastroplex will detect the most prevalent causative agents of bacterial gastroenteritis, while Carbaplex, an antibiotic resistance assay, will detect the most common gene families associated with resistance to carbapenems – often considered the antibiotic of last resort.
