SCREENING OF BLOOD DONORS
Transfusion scientists must be assured that the process of transfusing blood poses minimal risk to the patient and donor alike. Aside from the obvious need for blood to be carefully matched to avoid a possibly fatal transfusion reaction, it is essential that donors are carefully screened to avoid those who are ill or who may be harmed by giving blood, or whose blood poses a health risk because, for example, it is contaminated with certain viruses even though the donor shows no signs of ill health.
In the UK, blood is taken from healthy donors aged between 17 and 70 and is a voluntary and unpaid activity. Potential donors who are excluded from donation include individuals with HIV or hepatitis viral infections, as well as individuals who are at risk of becoming HIV and/or hepatitis virus positive, for example prostitutes, drug abusers who inject themselves with drugs, and individuals who have had sex with men or women living in Africa (Table 6.10). In addition, people with low hemoglobin levels (below 135 g dm–3 and 125 g dm–3 for men and women respectively), those who have had infectious dis-eases such as a cold or sore throat within the last seven days or viral infections such as measles, mumps, rubella, chickenpox, shingles or herpes simplex cold sores within the last three weeks. Other reasons for exclusion include the recent use of therapeutic drugs, for example aspirin, antibiotics, antihista-mines and antidepressants.
All donated blood is screened for a variety of infectious agent as shown in Table 6.11. Some tests are mandatory while others are optional. Optional testssuch as those for cytomegalovirus (CMV) are used when the blood is to be transfused into immunocompromized individuals.