Medicine in Miniature

A remote village in Kenya may be hundreds of miles from the nearest hospital, so what can its villagers do when one of their own comes down with a serious medical condition? That’s where point-of-care tests (POCTs)—portable devices that can diagnose patients on-site for HIV, tuberculosis, malaria, heart disease, and many other illnesses—come in.

“In the parts of the world where the disease burden is highest, microbiology laboratory capacity is often limited and inaccessible to most patients. Point-of-care diagnostic tests can provide access to state-of-the-art diagnostic support even in settings where health care infrastructure is minimal,” states a June 2012 report by the American Academy of Microbiology.

A POCT, per the formal definition, is a diagnostic test that does not require “permanent dedicated space” (i.e., a lab). It could be a test that a doctor administers right at a patient’s bedside, or even a home-administered one that the patient conducts on his or her own. POCTs have been getting a lot of credit in recent years for bringing state-of-the-art medicine out to patients who, for one reason or another, can’t make it to a hospital. Understandably, use of POCTs has been accelerating worldwide.

The American Academy of Microbiology’s report explores POCT usage in depth, starting with the demonstrable advantages. Conventional diagnostic-testing methods involve expensive equipment or personnel with advanced training—deployment is not always doable in remote places where electricity is not always available and there is no one around to maintain the hardware.

Also, the conventional methods require time. The physician collects a sample (blood, urine, etc.) and submits it to a lab for testing, which could take days or even weeks—too long for some patients, whose illnesses might necessitate fast-as-possible intervention. Fortunately for them, POCTs process samples at the molecular level to deliver diagnoses in mere hours or minutes.

Their comparative speediness is a huge win for disease prevention. An infectious disease will spread to fewer people if doctors detect it sooner. And non-infectious conditions, like diabetes and heart disease, are easier to treat when doctors catch them in their earliest stages. The report notes these points, and cites as an example the formidable effectiveness that rapid diagnostic HIV tests have demonstrated at combating the spread of HIV in South Africa.

“In clinics around the world, local health care workers are forced to make treatment decisions with inadequate information. Is this patient’s TB drug resistant? Is that child’s dehydration due to a parasite, or cholera? Asked what would help them in their jobs, rapid diagnostic tests to answer such questions would be high on local practitioners’ wish lists,” the report states.

The report sounds some caution, however: Context and place both matter. A health-care system that implements a POCT without giving enough thought to why it’s implementing it or what it expects it to achieve can run into some unintended and not-very-desirable consequences.

An example that the report points out: When South Africa decentralized tuberculosis testing from central labs to local clinics, the costs of testing increased by 70%. The conducting of tests are at multiple locations all across a country, instead of in a few established lab facilities, makes it all the harder to make sure that the tests are being administered properly, that results are being collected in full, and that they are all being stored securely.

Another unintended consequence is demand for more follow-up tests. For instance, if a POCT reveals that a large number of the patients are HIV-positive, the doctors will need to order more anti-retroviral treatments and tests of post-treatment viral counts. Can the health-care system act on the myriad new diagnoses that the POCT brings in? The system’s administrators had best answer this question before they put a proposed new POCT to work.

“The first order of business is rigorous evaluation of the overall cost-benefit ratio for any proposed POCT,” the report states.

Better POCTs may be on the way, though. According to the report, advancements in automation and miniaturization now going on in computer science, microbiology, and a multitude of other scientific fields could with time render POCTs everywhere more reliable and less expensive:

• Better detection of biomarkers (indicators of a given condition; reduced blood cell count is a biomarker for HIV, for instance). As we learn more about how disease processes work at the molecular level, we might figure out how to develop tests that not only measure the presence of a pathogen, but also the specific interactions of that pathogen with the host, the impact on health, and the implications for treatment.
• Connectivity that makes it possible to capture all POCT results permanently and in real time.
• Batteries and sustainable power, to ensure that systems can run even when the local electricity grids are spotty.
• Refrigeration and heat tolerance, so there will be fewer tests botched due to heat-sensitive testing chemicals being exposed to too much heat.
• Microfabrication—micro- and nano-arrays that can allow multiplexing of tests, facilitate quality control, reduce sample size, and lower the costs.
• “Microfluidic” devices, which allow for automation and miniaturization of multi-step tests.
• Artificially intelligent computer systems that would help providers to interpret the results and make treatment decisions.
• Technologies that allow samples to be smaller, easier to obtain, or more consistently processed.
• Communications links that enable the test developer, the regulatory agencies, the physicians, and the end users to all more effectively interact.

“The day when a clinic anywhere in the world could have the capacity to provide all of its patients with accurate diagnoses for virtually any infectious disease, along with appropriate treatment and timely follow-up, need not be too distant,” the report states.

Around the world, numbers of people in need of medical care keeps going up, but the numbers of trained health professionals and hospital centers can’t always keep pace. Doctors everywhere strain to help more patients, more efficiently. POCTs deserve much credit for, in their own small way, making this health-care challenge far more manageable.