Whether treating an accident victim or performing a planned surgery, one of the most basic things a doctor needs to know is his patient’s blood type. Knowing blood type information is essential because transfusion with the wrong type of blood can lead to an immunological response that can be fatal as the antigens and antibodies of the two different types of blood react.

There are more than 300 human blood types but most cause only minor reactions if mismatched. The two important blood types two differentiate are the ABO group and the Rhesus group that is marked either as positive or negative.

Conventional blood typing methods can take between 20 minutes and half an hour. This is why it is compulsory to have your blood type printed on your driver’s licence, so that paramedics and doctors do not waste time finding you blood type if you are in an accident and need blood. Blood samples are usually drawn from the patient and then a medical technician mixes the blood with a variety of serum samples of which the blood types are already known. The blood is then classified according to how it blood reacts with each kind of serum.

Scientists have now developed a new easy low-cost paper-based method of blood typing that takes just 30 seconds and can make all the difference in a medical emergency. They have coated anti-A antibodies to the left of a paper-based chip and anti-B antibodies to the right. A drop of blood is dropped at the centre of the chip. As the paper absorbs the blood and the blood moves through the membrane toward the ends of the chip, it touches the antibodies on either side. Depending on the type of blood, it will form clumps – to the left if it has antigen A, to the right if it has antigen B, on both sides if it has A and B antigens and no clumps if it is has no antigens or is “O” type. The paer is also coated with a due that turns brown when mixed with whole blood and teal when it counters only plasma left behind after blood cells clump in antigen-antibody reactions. This indicates that the corresponding marker – A on the left and B on the right – is present. If there is no marker, the blood will not clump and the dye will be brown.

Here is a video produced by Science on the innovation.