b. Work Outline for Incompatible Crossmatch. Preliminary investigation:
recheck ABO groups and Rh types of incompatible donors and recipients; recheck pilot
sample numbers against donor units and run an autocontrol with the antibody
identification panel.
c. Autocontrol Negative.
(1) Specific cold alloantibodies are suggested if reactions are detected at
room temperature; if reactions are weak or negative at 37C, by antiglobulin technique;
or if reactions are stronger at 18C to 15C, or lower. Under such conditions, do the
following:
(a) Identify the antibody or antibodies.
(b) If anti-A1 or anti-'Hl'(O) is identified, select blood on the basis of A
subgroups.
(c) If another specific antibody is identified, the RBCs of prospective
donors should be tested for this antigen with known reagent antiserum, (if available),
before transfusion. This is important because the antigenic strength varies among
donors in many blood-group systems. The patient's antibody may not be strong enough
to react with cells from units containing weak antigens. If antiserum is in short supply
and the patient's serum plentiful, crossmatch several units first and use the antiserum to
test only those units that appear compatible.
(2) Specific warm alloantibodies are suggested, if the reactions take place
at 37C, and/or are detected by antiglobulin technique. Do the following:
(a) Identify the antibody or antibodies.
(b) Test the cells of prospective donors for the corresponding antigens
with a known reagent antiserum.
(c) If the RBCs from only one donor unit react and the antibody
screening test on the patient is negative, do a direct antiglobulin test on the donor. If
the direct antiglobulin test is positive, quarantine the donor blood for further
investigation. If it is negative, test the patient's serum for antibodies directed against
low-incidence antigens.
(d) When RBCs from most donors react, there are two possible
explanations. There may be an antibody against a high-incidence RBC antigen or
multiple antibodies may be present. In either case, the patient's relatives, especially
siblings, may be compatible. If not, it may be possible to find compatible donors
through a Reference Laboratory, or Rare Donor File.
MD0846
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