Medical Device Link.

Diagnostics for Personalized Medicine

The approach to delivering healthcare is changing such that rapid diagnostic testing could become more prevalent. The objective now is to make the interactions between patients and providers more effective by taking an integrated and more targeted approach. Empowering the patients in this manner may not only increase efficiency but also deliver better outcomes.

In order to reduce the time spent in hospitals and improve overall patient outcomes, high-speed, robust, and sensitive IVD tests that can be used in various settings and not just in hospital laboratories should be developed. Whether it is an ambulance, a health clinic, a doctor’s office, or even a patient’s home, such decentralized settings should also be part of an IT network that links all participants in the healthcare cycle wherever they are located. This approach will ensure that patients are at the center.

However, current medical practices that are based on late-stage, hospital-based interventions constitute one of the most cost-intensive solutions for healthcare providers. In addition, changes in lifestyle habits, an aging world population, and the increase in patients getting medical information via the Internet put further pressure on the funding and management of healthcare systems.

Bringing IVD Testing to Patients

It is widely accepted that during the next 5–10 years, a shift toward earlier and minimally invasive treatments will be needed. While escalating healthcare costs have played their part in the growing worldwide demand for such change, the underlying catalyst for this development should be attributed to the decoding of the human genome. Scientifically, this discovery has transformed the overall understanding of and provided an increasingly deeper insight into the protein networks and signal transduction pathways involved in body homeostasis and pathological processes.

However, the challenge is not simply to achieve an accurate, scientific understanding of disease pathways at the molecular level. To be truly effective on behalf of patients, such knowledge must be combined with appropriate biomarker detection technologies and more flexible diagnostic platforms. Consequently, armed with this information, both pharmaceutical and IVD companies are actively developing new tools to help physicians target treatments to individuals and their diseases, thereby closing the gap between patients and therapies.

If the new global imperative is to speed up the diagnostic process and tailor it more effectively to individual patients and their circumstances, a practical and economical means of bringing IVD testing closer to patients should be found. Moreover, this ability should be available whenever instant diagnosis or real-time monitoring of therapies is required.

But it is not merely a question of introducing a new analyzer for use at the point of care. A more fundamental review of diagnostic practices is needed, particularly the optimal point at which IVD testing should be carried out for improved outcomes. The objective is to develop a decentralized testing system that complements and extends the existing hospital testing environment. Such a system should be effective in addressing a wide range of clinical environments, from monitoring chronically ill patients at home to the challenges of critical care in which the use of sensitive assays earlier in the patient care cycle could save lives. For example, the possibility of being able to run an accurate and precise troponin I assay in an ambulance on a potential heart attack patient.

Accuracy at Picomolar Levels

Low-cost, short time to result, and portable lateral-flow testing is currently standard for point-of-care systems. The glucose sensor is a good example, since it is small, rapid, easy to use, reliable, and economical. But in order for decentralized testing to become a reality, testing systems need to work using picomolar concentrations in blood and saliva, for example. At the same time, such systems must be able to conduct more-advanced and complex assay testing.

Philips (Eindhoven, The Netherlands) is developing a new generation of handheld diagnostic devices that offer disease-specific testing at the protein level and can be performed at a time and place convenient for patients. As a manufacturer of point-of-care technologies, Philips starts its research and development by investigating currently available systems (in this case, handheld diagnostic platforms) and determining their limitations. At the same time, the needs of patients and healthcare providers should also be considered. By doing so, resources can be allocated and concentrated more effectively on what is needed to develop a rapid diagnostic testing platform that can run robust and sensitive assays from minute sample volumes in a decentralized setting.

Key requirements for new handheld diagnostic technologies at different clinical testing stages include the following three areas:

• Preanalytical: Noninvasive easy-to-use methods, small sample volumes, identification on cartridges.

• Analytical: Lab-quality results, multianalyte testing.

• Postanalytical: IT connectivity, clinical decision support.

Preanalytical: Small Sample Volumes

For the next generation of handheld testing devices to be effective in a modern decentralized setting, they should be easy for nonlaboratory professionals to use and should not require special training. This requirement is essential for bringing new tests for personalized healthcare successfully to the IVD market. Any solutions therefore have to meet the waiver criteria established by the Clinical Laboratory Improvement Amendments (CLIA).

For the initial diagnostic applications of its Magnotech technology, Philips focused on saliva and blood. The company found saliva particularly interesting because of the substantial research on saliva biomarkers during the past five years. For example, the need for a simple saliva test that could help clinicians identify those patients who are most at risk of a life-threatening stroke.

New research by medical experts in The Netherlands and Germany, which was recently published in the Journal of Clinical Endocrinology and Metabolism, suggests that strokes could be prevented if clinicians routinely tested patients’ saliva. The study showed that high levels of the hormone cortisol in saliva may be directly linked to the build up of fatty deposits in arteries carrying blood to the brain. Such studies have already identified promising future saliva applications.

For blood applications, Philips learned that the ability to get accurate measurements from small blood volumes (i.e., a fingerprick of blood) is crucial. Another important requirement for the preanalytical stage is that the device should have a fail-safe function for recognizing system failures. One example is an alert when test cartridges have expired or the sample volume is insufficient.

Analytical Requirements

For a decentralized approach to succeed, innovative diagnostic technologies should offer speed and ease-of-use, a wide-ranging and flexible test menu that requires only minute sample volumes, and the accuracy and precision often associated with hospital lab systems.

Existing laboratory-based blood protein assays typically require a significant amount of fluid handling (e.g., pipetting, reagent mixing, centrifuging), resulting in complex equipment setups. In addition, the volume of blood needed often involves a skilled phlebotomist or nurse to draw blood samples from patients. In contrast, a new generation of rapid diagnostic tests should be able to deliver consistent results from only picomolar concentrations of an analyte in sample.

The challenge for Philips’ scientists was to develop a compact, handheld biosensor that is sensitive enough to detect substances such as hormones, drugs, proteins, and nucleic acids. The concentrations of such substances are 600 million times lower than those required to measure glucose satisfactorily using existing handheld device technologies. In addition, from an analytical point of view, a multi-parameter approach is necessary for a realistic patient-centered service to be delivered. Therefore, another key requirement of any new rapid diagnostic technology is the ability to run several analytes on one cartridge.

Postanalytical: IT Connectivity

Implementing a strategy of patient-centered medicine requires new technologies to deliver analytical requirements and address preanalytical needs. Consequently, the ability to transfer data in a fast and reliable manner is fundamental.

Accordingly, users should be able to transfer data to clinicians early and quickly enough so that immediate, optimal actions can be taken. Rapid diagnostic testing at the patient’s bedside can give feedback on a therapy’s effectiveness in minutes. In the case of patients suffering severe toxic effects, the opportunity for a rapid delivery of results could save lives.

The same applies to other potentially life-threatening conditions. For example, 5 million people in the United States suffer chest pains annually, but only 10% are immediately diagnosed as suffering myocardial infarction, and another 10% end up not having a heart attack. The remaining 80% must be monitored for up to 24 hours in a hospital to assess their conditions. However, the ability to monitor troponin levels earlier (e.g., in an ambulance) and then use connectivity to facilitate rapid clinical decision making could significantly affect costs and the deployment of medical resources.

To make this ability come to fruition, the different testing stations (i.e., conventional automated laboratories and new mobile handheld systems) would need to be part of a diagnostic network, using wired or wireless connectivity and sophisticated healthcare informatics solutions to store and assist in interpreting the data. Such clinical decision support systems and data mining would allow faster and more-accurate disease management that would benefit both patient outcomes and healthcare budgets.

The Magnotech Technology

The ever-increasing need to move testing out of the laboratory and into the field will be made possible by using highly integrated handheld or desktop IVD testing equipment. In this area, a new disposable biosensor technology developed by Philips that uses magnetic nanoparticles to measure target molecules is showing some promise as indicated by the initial results from proof-of-concept studies.

The Magnotech technology is integrated into a disposable biosensor cartridge that is inserted into a handheld analyzer (see Figure 1). The magnetic nanoparticles are preloaded into the cartridge when it is manufactured and are automatically dispersed into the sample as the cartridge is filled with a single drop of blood or saliva. Once the cartridge is filled, no other fluid movement is required.

The disposable cartridge is constructed entirely from plastic components and has no moving parts or embedded electronics. Contained in the unit itself are all the elements, electromagnets, optical detection system, control electronics, software, and readout display that are needed to deliver test results.

While this technology is in its early stages of development and still undergoing rigorous testing, its quickness, ease of use, robustness, and accuracy could address the requirements of critical-care environments by speeding up the diagnosis of life-threatening diseases. This technology would offer the potential of running sensitive IVD protein tests in various settings outside the lab or even in the home. Philips expects to publish more definitive research findings on the technology’s performance later this year.

The disease areas that Philips is focusing on for this technology are cardiology, oncology, women’s health, and infectious diseases. Potential diagnostic applications for this technology can been seen in all these areas. For example, measuring very low concentrations of biomarkers for diagnosing cardiovascular disease currently requires laboratory analysis and large sample volumes, and takes 30–60 minutes for test results. The Magnotech technology has been developed such that magnetic nanoparticles are used to measure target molecules in picomolar concentrations in blood or saliva in a few minutes. Depending on the application, the test time can be 1–5 minutes.

How the Technology Operates

The active area of the Magnotech’s biosensor is sufficiently large such that it can be spotted with ligands for several different proteins, thereby opening up the possibility of performing multiple assays in a single operation. In addition to performing a sandwich assay, the technology can be adapted to carry out other types of assays (e.g., competition assays) that may be suitable for detecting drugs of abuse and other small molecules in body fluid samples.

Philips has prototyped the Magnotech system to this stage of integration, and tests have shown that it is capable of detecting protein concentrations down to subpicomolar levels.1,2 For example, in the proof-of-concept testing for the cTnI assay, concentrations as low as one picomolar were detected in blood plasma in less than 5 minutes.

The entire assay process is executed by a controlled movement of magnetic nanoparticles in the cartridge using external magnetic fields. The magnetic nanoparticles are coated with appropriate ligand molecules, which enable them to bind to target protein molecules in the blood sample (see Figure 2). After a short time, typically about 1 minute, a large fraction of the target protein molecules are bound to the surface of the magnetic nanoparticles.

A small electromagnet under the cartridge then generates a magnetic field that attracts all the magnetic nanoparticles to the biosensor’s active surface. This surface is coated with ligand molecules that bind to a second binding site on the target protein. As a result of this magnetic attraction, the surface concentration of the target protein is significantly increased, which speeds up the binding process.

The target protein molecules end up locked in a sandwich between the active surface on one side and attached nanoparticles on the other (see Figure 3). An electromagnet above the cartridge then generates a magnetic field that pulls unbound magnetic nanoparticles away from the active surface (see Figure 4).

Through this process, a fast and controlled separation between bound and unbound magnetic nanoparticles is achieved, which replaces traditional washing steps. Because each magnetic nanoparticle that remains on the surface is bound there by a target protein molecule, the number of nanoparticles remaining at the surface is a measure of the target protein concentration in the blood sample.

Optimizing Performance of Different Assays

At the final step, the number of bound nanoparticles is measured using an optical technique based on frustrated total internal reflection. Illuminated at the correct angle, light hitting the underside of the sensor’s active surface is normally reflected without any loss in intensity (total internal reflection).

However, when nanoparticles are bound to the opposite side of the surface, they scatter and absorb the light, reducing the intensity of the reflected beam. Such intensity variations in the reflected beam, which correspond to the number of bound nanoparticles, are detected by a complementary metal-oxide semiconductor (CMOS) image sensor (see Figure 5). CMOS is both a particular style of digital circuitry design and the family of processes used to implement that circuitry on integrated circuits.

The magnetic actuation technology is the key, and being able to manipulate it is a major advantage since it allows the ability to optimize the performance of different assays.

Proof-of-Concept Findings

Philips has demonstrated proof-of-concept for its biosensor technology in various biological assays, including sandwich assays for detecting cardiac troponin I (cTnI) and parathyroid hormone and inhibition assays to detect several drugs-of-abuse molecules (e.g., morphine).1,2 The morphine assay represents the first application for the technology in drugs-of-abuse testing.

During these proof-of-concept tests, the biosensor technology sped up assays by a factor of more than 100 when compared with simply letting the nanoparticles diffuse to the sensor’s active surface. Furthermore, the magnetic actuation technology improved ease of use by eliminating fluidic washing steps. With cTnI, the assay was detected in picomolar concentrations in less than 5 minutes.

Conclusion

By 2020, the IVD industry should expect to see a shift away from acute care and late interventions to earlier and minimally invasive treatments that are tailored more specifically to a patient’s individual needs. In turn, diagnostic testing will need to be carried out in various decentralized settings. Testing at an earlier stage in the disease cycle will also offer the potential to save more lives. In addition, such earlier testing will be more convenient for chronically sick patients, improving their quality of life by allowing monitoring of their conditions at home or locally, rather than requiring hospital stays.

This new approach provides an opportunity for rapid diagnostic testing to play a more significant role in the patient care cycle. What will make this opportunity possible, and at a practical cost, is the availability of rapid, easy to use, robust handheld technologies that can safely take the testing environment to patients. Such platforms must deliver the level of sensitivity required for accurate measurements, from the smallest possible sample, and with the precision and accuracy of hospital laboratory systems.

IT connectivity, including the use of home telemonitoring facilities, will also be needed to link all the elements involved in the care cycle. Such connectivity will speed up the flow of vital medical information between patients and clinicians, improving the outcomes for the patient and overall efficiency.

Until recently, magnetic assay techniques were confined to the clinical laboratory. In combination with nanoparticle technologies, the Magnotech technology offers the prospect of running sensitive assays like troponin and parathyroid hormone at the point of care.