NHSN Biovigilance Component
Hemovigilance Module Surveillance Protocol v2.8
February 2023
Delayed hemolytic transfusion reaction (DHTR)
Note: Report all hemolytic reactions, including when the recipient is intentionally transfused with
incompatible blood components.
Positive direct antiglobulin test (DAT)
for antibodies developed between 24
hours and 28 days after cessation of
transfusion
AND EITHER
Positive elution test with
alloantibody present on the
transfused red blood cells
OR
Newly-identified red blood cell
alloantibody in recipient serum
AND EITHER
Inadequate rise of post-transfusion
hemoglobin level or rapid fall in
hemoglobin back to pre-transfusion
levels
OR
Otherwise unexplained appearance
of spherocytes.
Probable:
Newly-identified red blood cell
alloantibody demonstrated between
24 hours and 28 days after cessation
of transfusion
BUT
Incomplete laboratory evidence to
meet definitive case definition criteria.
NOTE: Patient may be asymptomatic
or have symptoms that are similar to
but milder than AHTR; symptoms are
not required to meet case definition
Medical intervention (e.g.
symptomatic treatment) is
required but lack of such would
not result in permanent damage
or impairment of a bodily
function.
Severe:
Inpatient hospitalization or
prolongation of hospitalization is
directly attributable to the
adverse reaction, persistent or
significant disability or incapacity
of the patient occurs as a result
of the reaction, or a medical or
surgical intervention is necessary
to preclude permanent damage
or impairment of a body function.
Life-threatening:
Major intervention required
following the transfusion (e.g.
vasopressors, intubation, transfer
to intensive care) to prevent
death.
Death:
The recipient died as a result of
the adverse transfusion
reaction. Death should be used
if death is possibly, probably or
definitely related to transfusion.
If the patient died of a cause
other than the transfusion, the
severity of the reaction should be
graded as appropriate given the
clinical circumstances related to
the reaction.
Not Determined:
The severity of the adverse
reaction is unknown or not
stated.
No other explanation for symptoms
or newly-identified antibody is
present.
Probable:
An alternate explanation for
symptoms or newly-identified
antibody is present, but transfusion is
the most likely cause.
Possible:
Other explanations for symptoms or
newly-identified antibody are more
likely, but transfusion cannot be ruled
out.
DHTR is suspected, but reported
symptoms, test results, and/or
available information are not sufficient
to meet the criteria defined above.
Other, more specific adverse reaction
definitions do not apply.
Evidence is clearly in favor of a
cause other than the transfusion, but
transfusion cannot be excluded.
Ruled Out:
There is conclusive evidence beyond
reasonable doubt of a cause other
than the transfusion.
Not Determined:
The relationship between the
adverse reaction and the transfusion
is unknown or not stated.