Harry Potter and the Order of Phlebotomists
A new blood type test has been developed that takes a page right out of Tom Riddle’s diary. Instead of writing on a page and receiving an answer, blood is washed over the paper and the letter corresponding to the blood type is activated.
Antibodies that are specific to each particular blood type are immobilized on the page, and when blood is washed over them, it sticks. The result is an easy-to-read, foolproof check for hospitals and mobile units.
No word on if it can detect mudblood.
(via Monash University)