What is possible with the blood test?


October 25, 2021 – Once valued at over $ 9 billion, it looked like Theranos would change the world of routine blood testing. Their claim was revolutionary: using blood from a finger prick, they could perform over 200 different tests. By going to a local pharmacy, someone could get tested without having a blood test and receive the results within hours rather than days. Additionally, Theranos said dozens of tests could be done on a single drop of blood, and that those tests would cost a fraction of traditional lab work.

But famously, Theranos’ house of cards has collapsed. The microwave-sized machine that supposedly could perform these tests, dubbed “Edison,” just didn’t work. What came as a shock to Silicon Valley and the investment world came as no surprise to those in the blood testing industry.

“It was like saying you could build a flying car that’s also a submarine, for the same price as an entry-level Toyota,” says Sheldon Campbell, MD, PhD, professor of laboratory medicine at the Yale School of Medicine.

Unlike in the world of computer technology, where a breakthrough can revolutionize the entire field, advances in blood testing are more stable and slower, like in the auto industry, says Campbell. While the auto industry has developed hybrid and electric vehicles, the foundations of a car have remained the same.

“The powertrains haven’t changed and the tires haven’t changed,” he says. “It’s a fairly mature technology.

Likewise, the process of blood testing is evolutionary rather than revolutionary.

When you do blood tests, the technician uses a needle to draw blood from a vein in your arm into a blood collection tube. Each tube collects between 1/2 and 1 teaspoon of blood, and the technician will fill one to more tubes during collection, depending on the number of tests prescribed by your doctor. This gives lab technicians a lot of work, and doctors may even order additional testing after a sample is taken.

About half of the blood is made up of red and white blood cells, while the other half is liquid. Most diagnostic tests use the liquid part, which means that only half of a standard sample is usually used for testing. You can also use blood from a finger prick, also known as a hair sample, for the test, but this can be more difficult. These samples – a few drops of blood – are 30 to 100 times smaller than your standard blood test. Unlike blood taken directly from a vein, capillary blood is mixed with fluid from the tissues, which can contribute to an inaccurate result.

For simpler tests like checking blood sugar, something people with diabetes do several times a day, using a small amount of blood from a finger, works very well. In fact, the most advanced blood glucose meters can even produce accurate results with a fraction of the blood needed for a typical hair sample.

“You are literally able to take the capillary sample, place it on your test strip, put it in your device, and this simple one-step chemical reaction takes place in this test chamber so you can get a measurement. blood sugar levels, ”says Kimberly Sanford, MD, president of the American Society of Clinical Pathology.

But moving more complicated tests that require multiple chemical reactions from central labs to clinics is getting trickier, Sanford says. Running multiple tests on a few drops of blood also adds additional engineering challenges, as a certain amount of blood is required for each result.

Diagnostic tests performed outside the lab, also known as point-of-care tests, are also more expensive than tests performed in a centralized lab. While these larger labs are designed to handle multiple samples at a time, point-of-care testing is performed one at a time.

To really get your money’s worth, testing should be easy, fast, and most importantly, accurate. Unless these office tests can provide clinicians with all the information they need to make a medical decision, it makes more sense to send samples to a lab.

“No point-of-care test, no matter how simple, is easier than checking one more box on a lab order form,” says Campbell.

But despite these hurdles, pieces of lab tests have made their way to clinics and bedside care.

“These are similar technologies to what we would use in the main lab on larger analyzers, but they miniaturize them and make them more portable,” says James H. Nichols, PhD, professor of pathology, microbiology and immunology at Vanderbilt University. Nashville Medical Center.

Advances in microfluidics – systems that process very small amounts of fluid for testing – have made it possible to perform several diagnostic tests on a few drops of blood, but not as many as Theranos had promised.

Abbott Laboratory’s i-STAT, for example, a portable blood analyzer with single-use test-specific cartridges, can provide multiple results from a standard sample per finger prick. Their Chem 8+ cartridge can provide results for nine metabolic measurements with a few drops of blood. To perform a test, the user places two or three drops of whole blood on the test cartridge, which is then inserted into the analyzer. A new test cartridge is used for each patient.

The i-STAT provides precise laboratory tests for blood gases, electrolytes, chemicals, coagulation, hematology, glucose and cardiac markers, an Abbott spokesperson said. Results are available in 2 minutes.

Although the device was designed for emergency care settings, it is now also used in healthcare salons, medical tents at events and many other mobile care facilities, Nichols said.

A few tabletop blood chemistry analyzers that perform these same types of tests are also available for emergency care as well as outpatient clinics. The Piccolo Xpress, for example, a portable analyzer the size of a shoebox, can perform up to 14 tests on a finger prick blood sample and provide results in 12 minutes.

The complete blood count, a common group of tests that counts the number of white blood cells, red blood cells and platelets in your blood, has also started to make its way into primary care and other outpatient clinics, Nichols says. With a few drops of blood, a clinician can get results in 3 minutes or less.

In the future, “there will also be more infectious diseases [testing] move from the main lab to the community, ”says Nichols, which is in part driven by the importance of rapid COVID-19 testing. For example, the development of additional rapid and easy-to-use tests for diseases more common outside the United States, such as malaria and dengue fever, could help improve access to laboratory diagnostics in developing countries, says -he.

“It will be an evolutionary process,” says Campbell, as pieces of lab testing continue to be adapted to faster, portable technologies. “And it will work both ways. The point-of-care market is clearly expanding and people are coming up with smart ideas and ways of doing things at the point-of-care, but the lab side won’t be static either, ”he said. “They’re going to kind of grow towards each other.”

About Hector Hedgepeth

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