The primary tests recommended by the World Health Organization (WHO)are  four in number. They are -

•  Surface Antigen(HbsAg)  for Hepatitis B

•  Antibody to Hepatitis C

•  HIV antibodies( for subtypes 1 and 2)

•  Serology test for Syphilis

  In 2006, a WHO survey revealed that in 56  of 124 countries where the survey was carried out  these basic tests were not done. Besides these core tests recommended by the WHO a variety of other tests are also carried out  depending on the local need. Some of these include  tests for variant Creutzfeldt-Jakob Disease (v CJD), West Nile Virus, cytomegalovirus and the HIVnucleic acis test (p24 antigen) that may help to detect a recently infected donor. The cytomegalovirus has negligible effect on a healthy recipient but may prove to be harmful on immuno-compromised patients, infants or  pregnant women.

It is also mandatry that blood donors should be free of fever  a fortnight prior to donating blood. They should also be free of  diseases such as Malaria and Filaria.

Cross matching is also carried out before transfusions. Here the plasma of the recipient is tested for antibodies against the antigens on the red blood cells of the donor blood. If agglutination takes place, the blood is not compatible and transfusion cannot take place. If there is no agglutination the blood can be transfused.

In case of emergency, however, ABO and Rh compatible blood is used for transfusion, which may be non cross - matched.