The basic idea is simple.
A drop of blood is placed on the surface of a gold electrode. Loose, single strands of DNA are mixed with the blood. If these strands find their complimentary, surface-attached DNA strands, they will bind to each other and a detectable electrical current will flow. If antibodies are present in the blood (i.e., antibodies corresponding to specific segments of DNA in the mixed sample), the DNA strands will not bind to form their characteristic double helix, and the electrical current will drop. (J Am Chem Soc 2015;137:15596; http://bit.ly/1LeuGb8.)
The experiment is brilliant for many reasons. By combining elements of physics and chemistry, this set-up turns out to be a simple, fast, and cheap way to detect disease. Very little equipment is needed to run the tests, the results take minutes to obtain, and each test only costs a few dollars to run. According to an article on CBC News, “The electrodes used to detect the electrical current can be had for five to ten cents each, and creating the necessary DNA sequences can be as cheap as ten dollars for a large enough strand to run thousands of tests.” (Sept. 25, 2105; http://bit.ly/1iQ6tM6.)
Not only would the measured current tell us if the antibodies being tested are present, it would also tell us the relative quantity of antibodies in the sample of blood. Scientists at the University of Montreal and the University of Rome discovered that “the drop [in electrical current] is so precisely measurable that the test can even be used to determine how much antibody is in a sample, instead of simply indicating its presence or absence.”
The applications of this study are limitless. It will allow for point-of-care (POC) testing for thousands of antibodies. We will be able to test for a whole host of viral, bacterial, parasitic, or autoimmune diseases simultaneously using a single drop of blood, obtaining the results within minutes. That same sample could also help us measure specific amounts of drug metabolites in the blood, allowing a practitioner to tailor the amount of antibiotic or chemotherapeutic agent given to a patient undergoing treatment.
The current arsenal of blood tests used in the emergency department is extremely limited. We routinely order CBC, BMP, LFT, lipase, troponin, CPK, and coagulation profiles, but these tests rarely help us diagnose specific diseases. They can help us determine if a patient has anemia, electrolyte imbalances, liver disease, renal failure, pancreatitis, or a myocardial infarction, but they can't identify the precise cause of illness.
The new POC test will revolutionize the way we practice medicine. Instead of telling a patient who presents to the emergency department with cough, congestion, and rhinorrhea that she may have a viral infection, we'll be able to tell her the exact viral strain she has, how much of the virus is currently circulating in her system, and whether she has a co-infection. This will, in turn, cut down on the rampant, inappropriate practice of prescribing antibiotics for viral infections. More importantly, it will help physicians recognize potentially lethal outbreaks of viral infections months before our current system can detect them.
Plethora of Diseases
Overtesting is generally a bad thing. It's expensive, time-consuming, and unnecessary. False-positive results often lead down a slippery slope of further testing, wrongful diagnosis, and potentially dangerous treatment. Opponents of overtesting will point out that this new POC assay is overkill.
They will state, rightfully so, that medical management for a patient who presents with symptoms of a common cold will be the same whether we can identify the particular viral strain causing the patient's symptoms. But this new POC assay is quick and cheap. Because it uses DNA technology, it has the potential for being highly sensitive and highly specific.
When you consider the plethora of disease processes out there, the myriad microorganisms that cause human infection, and the number of autoimmune illnesses that lead to debilitating disease, we need something like this new POC test in our arsenal. As emergency physicians, we are often forced to make clinical decisions with limited data. Our job is to rule out life-threatening illness, but our patients also expect us to arrive at a specific diagnosis.
We often disappoint them with our explanations of their symptoms when we don't have a confirmatory test to make that specific diagnosis. Many of us find it frustrating to have to tell patients that we don't know the cause of their illnesses. This new POC assay may be an effective tool for putting an end to that frustration.
As a rule, overtesting is a bad thing. This new POC assay will likely be the exception.
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