Caitlin Smith has a B.A. in biology from Reed College, a Ph.D. in neuroscience from Yale University, and completed postdoctoral work at the Vollum Institute.
Point-of-care (POC) tests have evolved from a unique approach for gathering information to an almost routine, more efficient solution for patients to receive care without having to travel to different locations for lab work. Often POC tests can provide faster time to results, which translates into better patient care. Today many POC tests are available; they focus on everything from blood chemistry to HIV infection. Here is a glimpse into common areas of POC testing and the processes involved in developing new POC diagnostic tests.
Common POC diagnostic tests
Tests for POC have evolved to many different levels. Basic self-testing of blood pressure and body temperature, for example, is commonplace. More advanced technology makes it possible for diabetics to self-administer POC tests for blood glucose at home. Rapid tests for influenza and streptococcal (strep) infection are making it more efficient for doctors to treat patients while they are still at the clinic. Previously, physicians would prescribe antibiotics for a sore throat and then wait several days for test results—even if the pain was caused by a virus, not strep bacteria. “This tool has been helpful in the ongoing public health efforts to avoid overuse of antibiotics for infections that won’t respond, [which helps to slow] the development of antibiotic resistance,” says Kate Adams, director of clinical services business development at Jackson Laboratory.
Another commonly used POC test monitors hemoglobin when people donate blood. “A few drops of blood can give phlebotomists crucial information about the iron content of the donor’s blood and determine donation eligibility in less than two minutes,” says Adams. Other types of tests—pregnancy, basic metabolic panel and cholesterol, for example—are frequently used in clinics. Emergency rooms and critical-care units may use any of the above, as well as hematocrit and cardiac-marker tests and tests for blood gases and electrolytes, says Tom Koshy, senior director of medical and scientific affairs at Alere. Public-health groups might use POC tests for HIV screening.
Point-of-care tests are nearly always more convenient than conventional lab tests, but they are especially valuable when a physician and patient require a quick turnaround because their next action or treatment depends upon the test result. Examples include tests for pregnancy, glucose, coagulation and sepsis, says Thomas Schlumpberger, vice president of clinical diagnostics at Singulex. This is especially true during “myocardial infarction, wherein the sooner a high-sensitivity troponin test can be done, the better,” says Jerry O’Brien, CEO of Radisens Diagnostics. Rapid tests also can help protect hospital staff and caregivers. “Methicillin-resistant staph [MRSA] infections need to be detected quickly for the health and safety of the patient, as well as the patients and staff around them,” says Adams.
POC-test development
The process of developing a POC test typically begins with an existing test performed in a clinical lab. “It has to be done first in a lab research and development setting,” says Koshy, “to demonstrate that the analyte is valuable, and the test is valid.” If there is demand for the specific detection, researchers can adapt the test or introduce an entirely new technology to transform it for POC use. The modifications usually include miniaturization and optimization to perform the measurements without the use of large lab equipment. “Laboratory-developed tests often have lower regulatory hurdles,” says O’Brien, “[while] POC tests require in-built controls and calibrators to ensure consistently high levels of performance.”
Because POC tests must function as stand-alone units, they are usually more expensive than lab tests. The latter “take advantage of economy of scale, because you can do many at once with automation and lab infrastructure,” says Koshy. Thus the value of speed must be weighed against the potentially greater cost.
Other important factors include whether samples can be easily acquired from patients, via finger prick or urine or saliva collection, for example. Also, POC tests must be robust enough to withstand use by someone who isn’t a trained lab technician. And their accuracy must be similar to that of lab tests. “The expectation is that they be as close as possible, and some are just as good [as lab tests], but there is a performance trade-off of POC vs. lab tests,” says Koshy. It is important, he says, to consider how much performance you really need, and if it’s worth the extra cost.
Challenges in developing new POC tests
Reducing cost, maintaining accuracy and ensuring robustness are challenges for POC test developers. Adams notes that “smaller devices are typically more expensive to produce, yet the U.S. healthcare system reimburses for the result provided and does not increase simply because the site of delivery has become more convenient.” Engineering the tests is also a tall order. “Taking a technology that provides reliable test results and delivering similar quality in a much smaller device can be very challenging,” says Adams.
At times, target-of-interest molecules present a challenge. Koshy says there would be great demand for a POC test for parathyroid hormone (PTH), for example—if developers could create one. “During a thyroidectomy, someone has to run the patient’s blood sample to the lab, which may not be close, to measure the PTH level, then wait for the result while the patient is open the whole time,” he says. The ability to rapidly and efficiently perform a PTH test in the operating room would be extremely valuable. But unfortunately, “PTH is a compound with a lot of metabolites, and it’s very sticky, which make it hard to develop a POC test for it,” says Koshy.
Certain geographic locations also can benefit from POC tests. These include places “where conventional lab testing is not available, such as rural areas and sub-Saharan Africa,” says Koshy. Indeed, the availability of POC testing for infectious diseases in developing countries would make a strong positive impact. “POC tests provide hope for disease control in areas where it is now nearly impossible, where underdeveloped medical infrastructure leads to brief and inconsistent patient-physician encounters” says Adams. Organizations like FIND are trying to make this happen. For FIND, an international nonprofit organization funded in part by the Bill & Melinda Gates Foundation, the “primary focus is the development of diagnostics to address exactly this gap in the provision of effective healthcare for developing countries,” says Adams. POC tests are designed to improve the health of humans, wherever they happen to live; it’s a happy accident that the nature of POCs makes them amenable to use in developing countries. Over time and with continuing improvements to existing methods, the opportunity for more efficient and effective global health care will be possible.