Good thinking. Pre and post Type and screen were negative. Actually, the patient has a Thalassemia trait who received two RBCs exchange with no reaction. The third RBC however the patient encountered 9 out of 10 pain on the pain scale. The location of the pain was at the joints, knees, and back. Given Morphine; After 1/2 hr, pain when away. All three units were retyped, crossmatched. All checked out.