O my! Paper strip test determines blood type in just 30 seconds | New Scientist
A, B, AB or O: Do you know which blood type you are? A quick and easy test might soon be able to tell you and allow hospitals to rapidly administer the right blood in an emergency.
Your blood type is essential information if you ever need a blood transfusion, because mismatched blood can send the immune system into meltdown, and sometimes lead to death. But it can take 10 or 20 minutes to verify someone’s blood type by conventional methods – not including the time it takes to transport the blood to a lab.
For this reason, most emergency departments stock only type O blood, which can safely be given to anyone because it lacks the antigens that trigger immune reactions. However, this places pressure on supplies of O blood. “The demand is already extremely high and it’s getting higher,” says Janet Wong at the Australian Red Cross Blood Service, which collects blood donations in Australia.
Now Hong Zhang at the Third Military Medical University in China and his colleagues have developed a paper-based test that could be quickly performed at a patient’s bedside without specialised training or equipment. It would allow hospitals to give patients matching blood – whether it be A, B, AB or O, and make it more viable to keep supplies of more blood types.
Looks good on paper
The test relies on the antigens that are present on the surface of red blood cells. Type A blood contains red blood cells with A antigens, B with B antigens, AB with both, and O with neither. The presence of a separate D antigen determines whether the blood type is “positive” or “negative”, also known as rhesus positive or negative.
Blood also contains antibodies, which find and destroy invaders. If they detect antigens from foreign red blood cells, they can mount a catastrophic immune response.
Zhang’s paper strip is impregnated with a matrix of antibodies and dye, and when a drop of blood is applied, squares of colour develop as the blood spreads across the strip and reacts with the antibodies. For each antigen – A, B and D – a teal square shows up if it is a present, or a brown square if it is not.
When trialled on 3550 human blood samples, the low-cost strip was more than 99.9 per cent accurate, and only took 30 seconds to complete.
Zhang says the paper strip could be used in war zones or remote areas where there are no labs to test patients’ blood types. O blood is currently used in these contexts, but supplies are limited.
Wong says the test could alleviate reliance on O blood in emergency settings, but it might still be wise to keep big stores of O blood, “The benefit of only stocking O blood is that you can’t accidentally give the wrong type,” she says. A paper test might determine the correct blood to give, but human error could still lead to a mix-up – particularly in high pressure scenarios – she adds.
Zhang says the paper test could be developed into a cost-effective and robust universal blood-grouping platform. “We are expecting that we can see this product in the market within 1-2 years,” he says.