A drop of a patient's blood is placed on three slides…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A drop of a patient's blood is placed on three slides. On the first slide it meets anti-A serum, on the second anti-B serum and on the third anti-Rh serum. Clumps form on the first and the third slides only.
- What is the ABO group of the patient?
- Is the patient Rh positive or Rh negative?
- Which antibody is in the plasma of this patient?
- The patient needs blood in an emergency. Which ABO groups can safely give?
Need a reminder? The key ideaShow
A transfusion is safe when no antigen of the donor meets its antibody in the recipient. Group A has antigen A and anti-B. Group B has antigen B and anti-A. Group AB has both antigens and no antibodies. Group O has no antigen and both antibodies. An Rh negative mother with an Rh positive foetus makes anti-Rh antibodies after the first delivery.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) The cells clump with anti-A, so they carry antigen A. They do not clump with anti-B. The group is A.
Step 2. (b) The cells clump with anti-Rh, so they carry the Rh antigen. The patient is Rh positive.
Step 3. (c) The plasma holds anti-B.
Step 4. (d) The donors must not carry antigen B: groups A and O.
Answer: (a) A; (b) Rh positive; (c) anti-B; (d) A and O.
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