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Feature Articles : Apr 15, 2009 (Vol. 29, No. 8)

POC Testing Predicted to Transform Healthcare

Results Bolster Evidence-Based Standards of Care and Improved Medical Outcomes
  • Ian George

Recent advances in portable and automated molecular diagnostic systems will address the previously unmet need for decentralized, point-of-care nucleic acid testing. Rapid, accurate diagnostic systems suitable for a variety of clinical settings, from the bedside to the battlefield, will enable test-and-treat models of care and improve medical decision making.

The clinical and economic benefits to be realized include rapid results delivery, individualized treatment regimens, better patient compliance, and overall improvements in disease management. These will drive uptake and implementation of emerging molecular diagnostic capabilities.

Molecular testing describes the ability to detect the cause of pathology at a molecular level—to isolate and measure directly the nucleic acid of an infectious agent, for example, or detect a genetic mutation or heritable polymorphism. It brings increased sensitivity and specificity compared to conventional diagnostic methods such as antibody-based assays.

Nucleic acid detection requires isolation and amplification of DNA or RNA from biomedical samples. Polymerase chain reaction (PCR), the industry standard for amplification, delivers exquisite sensitivity. Implementing PCR-based tests at the point-of-care presents significant technical challenges. It requires integration of sequential nucleic acid isolation, amplification, and results calling on miniaturized instrumentation.

The holy grail of point-of-care molecular testing remains a low-cost, portable, automated, and CLIA-waived system that can accommodate a range of samples (blood, swab, urine), can perform multiplexed testing, and has a minimal logistics and training burden. Ideally the system would operate as reliably and reproducibly in outreach settings as in the central laboratory.

Defining the Need

Until recently, the concept of molecular testing has been associated with images of high-throughput instrumentation housed in centralized, high-complexity facilities and operated by skilled technicians. The multistep procedures required for nucleic acid purification and amplification demand precision, reproducibility, and controlled environmental conditions that are difficult to achieve with manual operations and problematic to export to point-of-care testing sites.

With existing molecular testing technologies, trained operators are needed to manage the protocols, minimize the risk of sample contamination, and interpret the results. Other limitations including processing times of many hours on high-throughput instrumentation, the need for frozen reagents, and a restricted menu of approved assays have confined the use of molecular testing methods to centralized diagnostic laboratory settings.

Yet the need for accurate point-of-care diagnostics is reaching a critical level, particularly for infectious agents. At present, in a typical microbiology laboratory the sample-analysis workflow based on traditional cell culture requires as long as three to four days to deliver a result to the clinician. In the event of a false positive or false negative result, the test may need to be repeated, adding further delays. Technician training and experience in cell culture techniques are essential for reliable results.

A new generation of PCR-based molecular testing platforms offers real-time diagnostic solutions with on-site results delivery to enable a single-visit test-and-treat paradigm. Consider a scenario in which high-risk patients brought into the emergency department could be tested on-site for methicillin-resistant Staphylococcus aureus (MRSA). This would dramatically improve efforts to treat and contain the infection. In the biodefense sector, localized testing would allow for implementation of rapid response and control measures in the event that a biological threat agent was detected.

Infectious diseases such as MRSA, Clostridium difficile, pandemic influenza, and SARS represent a real public health threat. Pandemic human influenza in particular has been given high political priority. In 2007, for example, the Ranger consortium received funding from the European Union Seventh Framework Programme to develop diagnostic and surveillance tools for seasonal and pandemic influenza.

Currently, molecular testing is confined to the high-complexity, centralized CLIA laboratories representing only about 10% of diagnostic laboratories. Next-generation molecular testing systems could be placed in a wide range of decentralized laboratories as well as many near patient settings including hospital and outreach clinics, pharmacies, prisons, universities, and pandemic testing sites.

The value of being able to put rapid molecular diagnostic capabilities directly into the hands of community-based clinicians, first responders, military personnel in the battlefield, and relief workers in developing regions and at the site of natural disasters or acts of terrorism is incalculable.

Furthermore, as pharmaceutical companies shift away from a strategy of delivering widely prescribed blockbuster drugs and toward a stratified drug development ideology and the production of targeted therapeutic agents, they are increasingly relying on molecular tests and companion diagnostics to guide drug development and treatment decisions. This paradigm shift will enable progress toward realizing the vision of personalized medicine.

The genetic testing market represents another opportunity for penetration by point-of-care diagnostics, allowing for earlier diagnoses, rapid adjustment of therapeutic protocols, and discontinuation of ineffective treatments. The ability to screen and quantify biomarkers associated with disease prognosis and predictive therapeutic response would aid in treatment selection and support the trend toward stratified medicine.

Beyond the human healthcare markets, the food industry would benefit from rapid at-plant pathogen testing to ensure the early and safe release of perishable foods and raw materials. At present in the food industry, the majority of pathogen tests are performed by culture, which takes days to return a result. Opportunities exist to provide automated molecular tests to the 40,000 worldwide food plants. In the veterinary sector, point-of-care diagnostics would facilitate in-field testing for early identification of animal pandemics and monitoring the spread of disease, allowing for rapid implementation of appropriate control and containment measures.

Combining sample preparation, amplification, and results calling into a single portable instrument has proven a significant technical challenge. This is especially true for infectious disease testing, which often requires preparation of a large sample to capture sparse concentrations of the target agent.

Available Systems

The competitive landscape for portable molecular testing systems is populated by several instruments with varied capabilities. Systems in development that provide automated operation include Enigma Diagnostics’ FL & ML systems, Idaho Technology’s Film Array, IQuum’s Liat Analyzer, Handylab’s Jaguar Platform, and Smiths Detection’s Bioseeq Portable Vet Laboratory, while Cepheid has placed almost 1,000 GeneXpert Systems for the diagnosis of hospital-acquired infections. All of these systems are real-time thermal cyclers with the exception of the Bioseeq Portable Vet Lab, which utilizes a form of end-point, asymmetric amplification.

The two main approaches for integrating sample preparation with real-time, quantitative PCR incorporate either a fluidics route or a strategy based on magnetic beads—or a combination of the two. The available platforms and systems in development differ in their ability to multiplex—to process one or more samples at a time in parallel, or to offer multiplexed assay capabilities. Ideally a portable molecular testing system would provide rapid sample processing, low cost of reagents, the ability to handle a variety of sample types, and clear, definitive results reporting.

Collaborative projects under way demonstrate the demand for reliable, easy-to-use, point-of-care molecular tests. One example includes a recently initiated U.K. government-supported program in association with the UK Centre for Hospital Acquired Infections at Nottingham University to develop a rapid, near-patient screening system for chlamydia, MRSA, and C. difficile, which would enable results delivery and initiation of treatment at the time of testing.

Projects such as this one represent only the tip of the iceberg with respect to potential opportunities for implementing rapid molecular testing technology across broad application areas in both the clinical and applied market sectors. In the future, the breadth of applications for molecular diagnostics and point-of-care testing will continue to expand as the results drive new evidence-based standards of care, improved medical outcomes, and demand for more effective therapeutic strategies.