Handheld antibody tester could reveal if you’re immune to COVID

The antibody testing device could be used to create personalized vaccine doses.

Researchers in Hong Kong have developed a new, palm-sized device for SARS-CoV-2 antibody testing, which could rapidly reveal an individual’s level of immunity.

The new device, published in Science Advances, aims to split the difference between the two current forms of testing: highly accurate but onerous lab-based testing, which requires a sizable amount of blood drawn from a vein, and far more convenient finger-stick tests, which only give you a yes or no answer about the presence of antibodies — not the level in your blood.

Using just a few drops of blood, the new device can test for the presence of antibodies and reveal the amount of antibodies in their system.

Multiple vaccines, infection-acquired immunity, and the normal fluctuations and waning in the immune system can leave people with “no clue about the status of protection by vaccination and its durability,” the researchers wrote in their study.

Lab-based antibody testing is accurate, but inconvenient; more convenient finger-stick tests only give you a yes or no answer about the presence of antibodies, not the level in your blood.

Their antibody testing device, designed to be easy to use and understand, aims to give people that status — and eventually be able to use saliva and nasal samples, so people can use it at home without having to stick their fingers.

“Our vision is to provide a device as simple as a rapid test but also provides as good accuracy as [conventional antibody testing],” lead researcher Ting-Hsuan Chen told the Daily Beast

“I usually make an analogy to a mercury thermometer. It’s a device you can see and take temperature precisely without any equipment and that everyone can use. We hope our device can be like that, simple to use and everyone can read without any ambiguity to get the results they need.”

Antibody testing 101: Antibodies are proteins created in response to specific infections, or vaccines, to neutralize viruses and call in immune T cells for reinforcements.

When you receive a COVID-19 vaccine, it teaches the body’s immune system to recognize a piece of the virus — the spike protein — and create antibodies against it.

But antibody levels wane over time, so it can be hard to know how well protected you are at any given time. Antibody testing can be an effective way to see if someone is likely protected. If the level of antibodies in the blood match the amount researchers know is protective — the “correlate of immunity” — you’re likely immune.

A better way: City University’s antibody testing device uses microparticles to check for the presence of antibodies in the blood, and determine how many of them there are.

The device is a small, rectangular chip with channels and a results window. Inside the chip are two different kinds of microparticles, magnetic microparticles (MMP) and polystyrene microparticles (PMP). 

If there are antibodies in the blood, they will stick to the PMPs. This, in turn, causes the PMPs to stick to the MMPs. Then the mixture is hit with a magnet.

The handheld antibody testing device is designed to be simple to use and understand.

“When an external magnetic field is applied, MMPs and PMPs-antibodies-MMPs are pulled to the sidewall of a test tube, leaving only PMPs freely suspended in the solution,” the researchers wrote.

In other words, only the paired microparticles signifying antibodies end up in the results window, where a little bar gives you a graphical representation of the antibody levels in nanograms per milliliter, the Beast reported.

When tested in 91 people, the test closely aligned with the gold-standard laboratory methods. 

Bringing antibody testing home: Antibody testing can be done in either sensitive mode, which can take 70 minutes, or rapid mode, which provides results in 20 minutes.

The team believes their device is “particularly suitable for the general public to routinely check immune protection at local clinics, testing booths at border entry control, or other public sectors, providing a solution for accelerating economic recovery without adding to the medical burden on health care systems.”

With refinement, it could also be used to help develop personalized vaccination doses and recommendations, based on factors like age and if the immune system is compromised, the Daily Beast noted.

Immunity’s moving goalposts: The rise of new Omicron variants, however, has highlighted a key concern for public health officials: the virus has mutated to partially escape antibodies from the original version of the virus, and vaccines based on it. 

That means that the level of antibodies needed to prevent infection is a moving target. A level that was enough to stop earlier versions may not be sufficient to stop Omicron or its descendants, so interpreting antibody testing results may require updates over time.

“For example, Omicron may need [a] higher antibody level,” Chen, the lead researcher, told Freethink.

“However, such [a] threshold is still under investigation. Once the thresholds for different variants [are] determined, our device would use the threshold to evaluate whether a person is protected or not.”

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