TYK33
All of the following concerning blood typing are correct EXCEPT:
A. The American Association of Blood Banks (AABB) recommends a type and screen be repeated if the sample is over 72 hours old
B. The sample can be used up to 14-30 days if the patient has never been pregnant or transfused in the last 3 months.
C. Repeat screening is required every week in infants
D. Cross matching is only required for transfusion of PRBCs
Answer
The answer is C. Repeat screening is not required in infants younger than 4 months of age due to decreased antibody formation from an immature immune system. In fact, some centers give every infant O negative blood (because the type and screen is unreliable in infancy). Antibodies are usually not present at birth but may arise in most individuals by about 6-8 months of age. In the first 6-8 months of life, infants are exposed to a variety of antigens (foods, micro-organisms, etc) which have antigenic characteristics that are similar and that are cross reactive with the blood group antigens/antibodies. These antigens can then provide the stimulation for antibody formation in infants who do not already have these antibodies. One example of this is Escherichia coli having type B like antigens. Any antibodies produced that react to the PATIENTS own red blood cells (B antigen for an A blood type patient) will be limited via self tolerance.
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