AstraZeneca, rHealth develop fingerstick test for low platelet count, a rare side effect of AZ's COVID vaccine

COVID-19 vaccine
The point-of-care diagnostic test uses the portable rHealth One analyzer and only 20 microliters of blood—a fraction of a drop—to measure platelet counts as accurately as the current gold-standard method, which requires a full venous blood draw, a cytometer and an impedance analyzer. (solarseven/ iStock/ Getty Images Plus)

Earlier this year, a study conducted by the University of Edinburgh found that people who received the COVID-19 vaccine developed by AstraZeneca and the University of Oxford were at a very slightly elevated risk of developing the rare blood disorder idiopathic thrombocytopenic purpura after receiving the jab.

Commonly referred to as ITP, the condition causes a sharp decrease in the number of platelets in the blood, which can in turn lead to an increase in bruising and bleeding, including internal bleeding. The study found that about 11 per 1 million doses of the Oxford-AstraZeneca vaccine resulted in the condition.

The chances may be slim, but in an apparent effort to address the issue head-on, AstraZeneca teamed up with rHealth to develop a diagnostic test that could measure platelet count at the point of care.

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It worked: According to a study published today in the journal PLOS ONE, the testing method developed by the partners was able to determine platelet count with accuracy levels comparable to those of the current gold-standard testing method developed by the International Society for Laboratory Hematology.

While the latter test typically requires a full venous blood draw and both a cytometer and an impedance analyzer—two bulky, expensive pieces of lab equipment—AstraZeneca and rHealth’s needs only a tiny blood sample obtained via fingerstick and the portable rHealth One analyzer, which clocks in at just over three pounds.

In the study, blood samples taken from both the fingertip and the vein were diluted and fed into the cytometry-based rHealth One device. Not only did both types of blood draw produce similar results—proving that platelet count could be measured using only the few drops of blood produced by a fingerstick lancet—but they also achieved “near-perfect correlation” with the ISLH method in samples containing a wide range of platelet counts.

Additionally, in contrast to the lab-locked ISLH method, because of the rHealth One’s small size, the researchers suggested that their test could ultimately be widely used at hospital bedsides and even in the home alongside the delivery of vaccines, chemotherapy drugs and other medications that can cause low platelet count, or thrombocytopenia.

“The rHealth technology shows that thrombocytopenia can be diagnosed accurately with our minimally invasive, point-of-care approach. It has the potential to provide optimal patient care when used together with certain vaccines and drugs,” rHealth CEO Eugene Chan said in a statement.

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This work with AstraZeneca marks the latest development in rHealth’s goal of building a consumer-centric analyzer that can test for a variety of conditions using only a few drops of blood.

That familiar-sounding mission may prompt a healthy dose of caution (and understandably so), but rHealth is working hard to prove that its technology is far more legitimate than Theranos’ failed Edison device.

To that effect, the company already has one regulatory clearance under its belt. In early 2018, it received a CE mark from Europe’s regulatory body for its fluorogenic Factor VIII test kit, which is used with the rHealth analyzer to test for factor VIII, a blood-clotting protein that, when found to be deficient or defective, is used to diagnose hemophilia.

The rHealth One and its accompanying tests have also received millions in government funding and support. Since 2019, for example, in addition to receiving multiple grants from the National Institutes of Health to further develop tests for factor VIII and COVID-19, rHealth has also supplied several of its analyzers to NASA to be assessed for potential use on the International Space Station.