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Transfusion Reaction Workup

Every year more than 5 million individuals in the United States are transfused with allogeneic and autologous blood components. In spite of extensive donor screening and laboratory testing, a small number of transfused patients experience adverse transfusion reactions. An adverse reaction is defined as any unfavorable event that occurs during or after a transfusion. The cellular or fluid portions of the blood, anticoagulant-preservative solution, metabolic by-products, and circulating or contaminant microorganisms may cause adverse reactions. 

When an adverse transfusion reaction occurs, medical, nursing and laboratory personnel must be prepared to recognize and treat them. Because the signs and symptoms of different types of adverse reactions overlap and their severity can vary considerably, all transfusions must be carefully monitored and stopped as soon as symptoms of a reaction appear. Early recognition is the key to minimizing serious complications. Signs and symptoms of a transfusion reaction include:

Signs and Symptoms of Transfusion Reactions

Nursing Action

For any acute reaction other than hives, the nursing or medical staff should take the following action:

1. Stop the transfusion immediately and disconnect the entire infusion set from the needle or catheter
2. Keep the IV line open with a slow drip of Normal Saline, using a new infusion set.
3. Check the blood bag label and paperwork against the patient's ID band to confirm that the patient received the correct unit.
4. Notify the attending physician so that treatment, if necessary, can begin immediately.
5. Take vital signs every 15 minutes until the patient is stable.
6. Notify the Transfusion Service & describe the signs and symptoms of the reaction.
7. Send the following items on a STAT basis:
   • Completed transfusion reaction form
   • Blood component bag with attached infusion set & IV fluids.
   • Post transfusion blood sample
   • Post-transfusion urine specimen

Laboratory Response

The Transfusion Service staff will immediately determine whether hemolysis has occurred. If possible, testing should be performed by someone other than the person who completed the original testing. Laboratory evaluation of a suspected hemolytic reaction can follow a hierarchic approach. For example, testing may be divided into Tier One and Tier Two. First Tier testing is designed to detect hemolysis, but cannot differentiate immune from other causes of hemolysis. Negative first tier testing rules out hemolysis. Second tier testing is performed if first tier testing indicates that hemolysis occurred. It is intended to establish the diagnosis of immune hemolysis.

Tier One Testing

Tier one testing encompasses:

1. Clerical check for procedural or identification errors
2. Visual check of post-transfusion plasma for hemolysis
3. Comparison of blood types on pre and post-transfusion specimens
4. Direct antiglobulin test on post-reaction sample

The detailed steps include:

1. Inspecting the label on the transfusion tag and blood bag and all other records to detect an error in identifying the patient or the unit of blood.
2. Checking the appearance of the blood bag, administration set and saline for discoloration or hemolysis.
3. Comparing patient’s pre and post transfusion specimens for proper identification.
4. Visually inspecting pre and post transfusion plasma for hemoglobin or bilirubin.
5. If hemolysis is observed in the post transfusion specimen, requesting another specimen to rule out mechanical hemolysis.
6. Performing an ABO & Rh type on the post transfusion specimen and comparing the results to the pre transfusion specimen results.
7. Performing a DAT on the post transfusion specimen. If the post DAT is positive, performing a DAT on the pre transfusion specimen.

Hemolysis in the post-transfusion sample, but not the pre-transfusion sample is suspicious of a hemolytic transfusion reaction. As little as 20 mg/dL of hemoglobin will make the plasma appear pink, while 50 mg/dL or more will make it appear red. This degree of hemoglobinemia corresponds to the hemolysis of 4 to 10 mL of RBCs. Hemolysis in both samples suggests that some other explanation must be sought (see nonimmune hemolysis section below).

If the DAT is positive on the post-reaction specimen, a pre-transfusion reaction sample should be tested for comparison. If the post transfusion DAT is positive, but the pre-transfusion DAT is negative a hemolytic transfusion reaction is possible. Since circulating antibody or complement coated red cells may be rapidly cleared, the DAT may be negative especially if the specimen was drawn several hours after the suspected reaction. If incompatible transfused cells have been partially destroyed, the DAT may have a mixed field appearance. The DAT will be positive if at least 10% of a patient’s red cells are coated with IgG.

If both the pre and post-transfusion DAT are positive, the test is not helpful in diagnosis of a hemolytic transfusion reaction, because the DATmay be the result of:

1. Autoimmune hemolytic anemia
2. Benign red cell autoantibody
3. Drug sensitization
4. Intravenous immune globulin (IVIg) infusion
5. RhIg administration
6. Transfusion of a DAT positive donor red cell unit.

No further investigation is necessary if:

1. The clerical checks match each other.
2. No hemolysis is observed.
3. Pre and post transfusion blood types are the same.
4. DAT is negative.

In this case, theTransfusion Reaction form is signed by the Clinical Laboratory Scientist and left for Pathologist review & interpretation. After the form has been signed, one copy is placed in the medical record and a second copy is kept in the Transfusion Service.

Tier Two Testing

If any part of Tier One testing is positive or the patient’s medical condition strongly suggests a hemolytic reaction, then Tier Two testing is undertaken.

1. Repeat ABO & Rh type, antibody screen and DAT on the pre and post transfusion specimens and blood from the unit in question.
2. Perform major and minor antiglobulin crossmatches on the pre and post blood specimens.
3. If results indicate a hemolytic reaction, immediately notify the patient’s physician and a pathologist.
4. Test the patient’s first post transfusion urine sample with a dipstick for hemoglobin. If positive, perform a microscopic urinalysis to rule out the presence of intact RBCs.
5. Measure patient’s post transfusion hemoglobin and compare it to the pre transfusion value.
6. Order a pre and post transfusion haptoglobin level.
7. Order a pre and post transfusion total and direct bilirubin and repeat in 4 to 6 hours.
8. Consult the pathologist to determine if additional tests are warranted.
9. If bacterial contamination is suspected, the following should be done:
   1. Notify the patient’s physician and the pathologist immediately.
   2. Perform a gram stain on blood from the blood bag in question.
   3. Ask Microbiology to set up aerobic and anaerobic blood cultures on blood from the bag (not from a segment) and any IV solution hanging with the unit.
   4. Ask the physician to order 2 sets of blood cultures on the patient.
   5. If Transfusion Related Acute Lung Injury (TRALI) is suspected
      1. Complete Tier One testing
      2. Consult the pathologist to determine if a granulocyte antibody should be ordered on the patient.
      3. Notify the Blood Center that supplied the unit so that they can:
         1. Review donor history.
         2. Perform a granulocyte antibody on the donor’s plasma.
         3. Defer the donor from future donations if TRALI is confirmed.
   6. Notify the FDA through MedWatch.

If ABO and Rh typing on the pre and post-reaction samples do not agree, there has been an error in patient or sample identification or testing. If so, another patient’s blood sample may have been drawn and incorrectly labeled, making it imperative to check the records of all specimens received at approximately the same time. If the donor blood type is not the same ABO type as the bag label, then an error has occurred in either labeling or processing of the unit.

If hemolysis is observed in the blood bag, red blood cells may have been hemolyzed because the unit was improperly transported, stored, warmed or mixed with a hypotonic IV solution.

In a hemolytic reaction, DAT may be positive and antibody screen negative. In this situation, a red cell eluate can be used for antibody identification.

Pre and post crossmatches should be performed, including the antiglobulin phase, to detect an antibody to a low frequency antigen or an error in pretransfusion testing. Whenever possible, the pre-transfusion crossmatch should be repeated with cells from a retained segment. If an incompatibility is found, a second crossmatch should be performed with the pre-transfusion serum and donor unit red cells to see if incompatibility was present prior to transfusion.

1. If both pre and post-reaction crossmatches are incompatible, an error was almost certainly made during pre-transfusion testing. The donor specimen used for the original crossmatch may have been taken from a different unit or the patient’s antibody screen was incorrectly read as negative.
2. If the crossmatch is incompatible with the post-reaction specimen but compatible with the pre-reaction specimen, anamnestic recall of antibody may have occurred. Antibody may have developed to red cells transfused in the preceding few days. Less likely, antibody may have been present in the transfused blood component and passively transfused.

Once an antibody has been identified, it is helpful to antigen type red cells from the transfused units to determine how many units were incompatible. The potential severity of hemolysis can be estimated from the number of antigen positive units transfused.