Investigation of a Delayed Hemolytic Transfusion Reaction (DHTR)

Transfusion services should have clear policies describing the required investigation of transfusion complications.

A Delayed Hemolytic Transfusion Reaction is seen days to weeks post-transfusion, and usually detected serologically with the direct antiglobulin test (DAT) showing a positive result.

Depending on the results of the initial investigation, the transfusion service will perform follow-up serologic testing according to its own policies and procedures. Some examples are outlined below.

NOTE: The expected results in a DHTR include the appearance of a"new" antibody and development of a positive DAT, although these may not always be detectable depending on the time of testing.

Positive Direct Antiglobulin Test (DAT)

To be valid, a DAT should be performed on an (EDTA) specimen. An EDTA specimen will prevent complement from binding in vitro due to a harmless cold autoantibody such as autoanti-I, an autoantibody, which many people have. If the DAT done on the patient's post-transfusion EDTA blood sample is positive:

• perform a DAT on the pre-transfusion blood sample for comparison (unless already done). If the DAT on the pre-transfusion specimen is also positive, and of approximately the same strength, the positive DAT on the post-transfusion specimen is not suggestive of a hemolytic transfusion reaction.

If the DAT on the pre-transfusion specimen is negative, a more complete investigation should be done, an example of which follows.

Monospecific DATs

If the post-transfusion DAT is positive with polyspecific antiglobulin serum, the DAT should be repeated with monospecific anti-IgG and anti-C3b/-d to determine the substances sensitizing the patient's red cells. The major purpose is to assess if an elution is worthwhile to identify antibodies that may be sensitizing the patient's cells.

Elution

An elution should be performed if a DAT using a monospecific anti-IgG is positive. The eluate is then tested with a panel to identify the antibodies involved.

Antigen type

If a specific antibody is identified, the patient's pre-transfusion specimen should be phenotyped for the antigen(s) corresponding to the antibody(ies) identified.