Mixed field w/ forward blood type testing

Medical Technologist often find themselves questioning if the forward type results are mixed field. A mixed field result occurs when a different type of blood is transfused into the patient. Patients are often given non-type specific blood. The patient may be a AB patient that may receive A or B red cells. This occurs when the blood bank has no AB red cells available. Patients that recently received a bone marrow transplant may also be transfused blood matching the bone marrow donor. The patient my have Anti- A1 antibody so they are given O red blood cells. All scenarios requiring out of group blood transfusion’s may ultimately lead to mixed fields in testing.

The technologist must determine if and when the patient received a out of group transfusion. For example if the patient has a anti A1 antibody and they may have received O units. Technologist often give O units to patients with anti A1 in order to avoid having to give A1 antigen negative units that are usually not available.  The technologist can expect to observe a mixed field in the forward typing of A since the patient has received O red blood cells.

As with all testing in blood bank patient history must be evaluated before determining if testing results are the result of out of group transfusion.

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