In severe trauma, doctors urgently need two readings: blood type, so that a transfusion is safe, and hematocrit - the share of red cells in the blood, which is used to judge blood loss or anemia. Hospitals have large analyzers for this, but they need electricity and trained staff. An ambulance, a disaster zone or a remote clinic often has neither.
A team led by Professor Chien-Fu Chen of National Taiwan University has proposed a simple alternative: a small plastic chip spun by a hand-powered centrifuge without electricity. About 3 microliters of blood from a finger prick is enough for the test. The work was published in the journal Biosensors and Bioelectronics.
When the handle is turned, the blood passes through winding channels pre-filled with reagents for groups A, B and Rh. If the blood matches, its red cells clump together and get stuck at the end of the channel at a gap about one tenth the width of a human hair. A red stripe forms, and the group can be seen at a glance. The length of the stripe also shows hematocrit: the more red cells, the longer the stripe - it is compared with a scale on the chip.
In tests on 21 samples from hospital patients, the results closely matched the readings of standard hospital analyzers. The readings remained stable at different handle speeds. The whole test takes about a minute.
"Our goal is to bring two vital blood tests out of the laboratory and into the hands of first responders, without electricity or special training," says Chen, a distinguished professor at the Institute of Applied Mechanics at National Taiwan University.
The authors stress that this is a prototype tested on a small sample. Larger trials are needed before the method enters practice.