What is the role of lab testing in the workup of delayed hemolytic transfusion reactions (DHTR)?

Updated: Sep 08, 2017
  • Author: Douglas Blackall, MD, MPH; Chief Editor: Michael A Kaliner, MD  more...
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The most reliable laboratory finding is a failure to observe the expected posttransfusion increase in blood hemoglobin level (approximately 1 g/dL/U) in the absence of bleeding.

In some cases, the loss of circulating red cells may be higher than would be expected if only antigen-positive cells were cleared. This phenomenon results from bystander hemolysis, which is caused by the deposition of activated complement on both donor and recipient RBCs.

Laboratory signs of hemolysis include elevated lactate dehydrogenase, indirect bilirubin, and reticulocyte levels and decreased hematocrit and haptoglobin levels.

Intravascular hemolysis is characterized by the presence of free plasma hemoglobin, free urine hemoglobin, and possibly hemosiderinuria.

The results of direct and indirect antiglobulin tests (ie, Coombs' tests) are often positive.

Alloantibodies can be eluted from RBCs, and their specificity can be defined. In the setting of hemolysis, sensitive elution techniques should be performed to identify alloantibodies, even if serum antibodies are undetectable and the direct antiglobulin test is only weakly reactive. In 15-20% of cases, patients with DHTRs have multiple antibodies; some may be detectable only by elution.

If possible, type the donor RBCs for the corresponding antigen(s) of interest and re-crossmatch them with the patient's serum, if segments from the transfused units are available.

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