Acute Hemolytic Reactions
LAB DIAGNOSIS: Making the lab diagnosis of an Acute Hemolytic Transfusion Reaction has one very simple prerequisite: you must first think of the diagnosis.
Seems obvious, doesn't it? Yet, many acute HTRs are ignored in the early stages, when you can really make a difference if you had a very high index of suspicion and worked the possible reaction up.
With that being said, once you actually entertain the possibility, some basic things emerge from the reaction workup.
First, the SCREENING TESTS:
Paperwork Check
Since these reactions are often the result of clerical errors, it is not uncommon to find an error when performing the paperwork check (i.e., unit intended for another patient, ABO incompatible unit issued in error, etc.)
Hemoglobin Check
Remember, as little as 5 ml of hemolysis can give visible free hemoglobin. Since most acute HTRs are intravascular, free hemoglobin is usually present, and is the most sensitive indicator of such a reaction. (See what a positive free hemoglobin test looks like)
Direct Antiglobulin Test (DAT)
The DAT checks for red cells coated with IgG and/or complement. In the setting of an acute HTR, the DAT is usually positive, but may be negative if all of the incompatible donor cells were destroyed (NOT an unheard of phenomenon in an overwhelming ABO-related acute HTR).
FORWARD to Diagnosis part 2
BACK to Presentation
Back to Acute Hemolytic Reactions
Back to Transfusion Reaction Types