Blood groups A, B, and O were described by Landsteiner in 1901¹ and the serological crossmatch between the blood donor and the recipient, as a means of preventing ABO incompatibility, was first described by Ottenberg in 1908.² In 1941, Rh antibodies were found to be the cause of haemolytic disease of the newborn. The earliest detected forms of anti-D antibodies were very strong and found by saline agglutination. The clinical importance of the discovery quickly led to the development by Coombs and others of the antiglobulin test.³ In what might be regarded in retrospect as a golden age of red blood cell serology, discovery of other clinically important red cell antigens followed quickly.

Extra effort was then put into the crossmatch, aimed at detection of atypical antibodies, with the result that by the 1960s red blood cell transfusions were being given only after extensive crossmatching performed in saline, at room temperature and body temperature, by enzyme methods, by albumin addition, and by the indirect antiglobulin test. Over the subsequent two decades there has been a slow but steady serological retreat until by the 1990s most laboratories were concentrating on a well performed indirect antiglobulin test alone for the detection of both atypical antibodies and ABO incompatibility.

If we consider the role of the crossmatch as a test for atypical antibodies it is clear that it has limitations. The donor cells, of varying age, are stored at varying haematocrit in a small plastic tag and usually diluted by eye to roughly the right cell concentration. The test is then performed once only and without a positive control.

When serologists were happy that all clinically important red blood cell antigens had been recognised it was possible to choose a red blood cell screening panel that covered all the important …