Blood tests for blood groups are very important, but are not always easy to interpret. In JK Rowling’s Harry Potter and the Chamber of Secrets, Harry writes a question and gets the answer in writing on the pages of a diary. A team of Australian researchers have developed a blood test, published in Angewandte Chemie, where the blood type results appear in writing, using paper with antibodies against antigens on the blood cells.

A blood test in plain writing