A new test can determine blood type in seconds, scientists say

Researchers say they have developed a cheap, easy test to determine a patient’s blood type with nearly perfect accuracy in a matter of seconds — an innovation that could help determine the blood type of patients in remote settings or conflict zones.

The new assay is able to pinpoint whether a person is type A, B, or O in just 30 seconds, and determine the blood type in full detail in about two minutes. That could allow for quicker action in providing safe blood transfusions or organ transplants. Results on the new device were published Wednesday in Science Translational Medicine.

Conventional tests to determine blood type take anywhere between 10 and 20 minutes. Other, newer technologies have cut that time down to to under five minutes. But until now, researchers hadn’t been able to consolidate the two-step process of typing blood into one quick, simple action.

There are three basic types of blood — A, B, and O. A person’s blood either does or doesn’t have a compound known as Rh factor on the surface of blood cells, hence the “positive” and “negative” blood types. The typical method for typing blood involves two steps: forward typing and reverse typing.

In forward typing, a patient’s blood sample is shaken up with antibodies found in type A and type B blood to see how it reacts. And in reverse typing, a patient’s serum — the liquid part of your blood, which doesn’t contain any cells — is mixed with blood that’s already been identified. Together, those steps can determine a patient’s blood type.

But the two tests can’t be run on the same sample simultaneously. The new assay can do forward typing and reverse typing at the same time. It does so by using a filter that separates the blood needed for forward typing from the plasma needed for reverse typing.

“The red blood cells will stop swimming while the plasma will go ahead along the strip,” said Hong Zhang, the study author and a researcher at Third Military Medical University in Chongqing, China.

The test relied on interactions between proteins in blood serum and a commonly used green dye. Each paper test strip housed antibodies that are able to recognize the antigens found in different blood types. The dye turned the test windows on the paper strip a different color depending on the blood type.

Zhang and his colleagues used the test to analyze 3,550 blood samples, which were obtained either using a blood draw or a finger prick. It was accurate more than 99.9 percent of the time — the only accuracy issues cropped up when testing highly uncommon blood types.