Whenever a candidate for transfusion has a clinically
significant antibody, whether currently detectable or detected previously,
all units transfused must first be typed for the corresponding antigen.
Antigen typing of the patient is also done to confirm
identity of an antibody when it is first identified.
Some prenatal workups include a request for antigen
typing of the father when the mother has an antibody, to predict the
likelihood of hemolytic disease of the newborn.
Because a small volume of patient cells is used, a
small lavender top (EDTA) or red top (clotted) tube is sufficient. The
sample used for the type and crossmatch may be used for antigen typing.
REAGENTS, EQUIPMENT, AND SUPPLIES
- Vial of reagent antiserum with manufacturer's
- Heterozygous positive control cell
- Negative control cell
- Other materials described in the manufacturer's
|NOTE: To ensure
accuracy of results, the direction circular enclosed with each vial of
antiserum must be followed closely. The amount of antiserum,
incubation time, and temperature, and type of procedure will vary from
lot to lot and from manufacturer to manufacturer.
- Select the vial of antiserum. There is commonly
special antisera available for the following antigens:
C, c E, e
Lewis a, Lewis b
Fy a, Fy b
M, N, S, s
- Select one cell known to be negative for the
antigen being tested. This can usually be a screening cell but can be an
identification panel cell as well. Record which cell you are using on the worksheet.
- Select one cell known to be heterozygous positive
for the antigen being tested. Use of a heterozygous cell ensures that the
antiserum is reactive with weaker expressions of the antigen. This will
usually have to be a panel cell. Record the cell number, lot number,
expiration date, and manufacturer on the worksheet.
- Prepare a washed 3% suspension of cells to be
tested. Check manufacturer's directions carefully - some methods call for
multiply-washed cells, including the positive and negative controls.
- Label the following tubes:
- NEG CONTROL
- POS CONTROL
- PT (or DONOR) TEST
- Add antiserum to each of the above tubes. (See
manufacturer’s directions for number of drops)
- Add one drop of the cells selected in #2 above to
the NEG control, and add one drop of the cells selected in #3 above to the
- Add one drop washed 3% patient or donor cells to be
antigen-typed to the TEST tube.
- Include a patient or donor cell control:
- label a tube CELL CONTROL
- add one drop Rh control
- add one drop of the cells to be antigen-typed
- treat this tube exactly as the test - except don't
add reagent antiserum - the Rh control albumin is replacing this
- Follow the manufacturer's directions enclosed
with the vial of antiserum. Treat test cells, the cell control, and
positive and negative controls identically from this point on.
- If a Coombs procedure is used, be sure to confirm
all negative results with Coombs Control Cells.
- Record all results in the proper columns on the
antigen typing worksheet.
NOTES AND PRECAUTIONS
- For the test to be valid, the controls must be as
- cell control: negative
- positive control: strong positive (at least 2+)
- negative control: negative
- False positives may result if the cells being
tested have a positive DAT. This will be detected by agglutination in the
cell control tube. The antigen typings on these patients will give false
positive or possibly mixed-field results. Specialized procedures may be
used to remove the antibody from the patient cells so that antigen typing
may be preformed. See the AABB Technical Manual.
- Be sure to perform antigen typings on a
pre-transfusion sample, if possible. Antigen typings on a
recently-transfused patient may produce mixed-field or false-positive
AABB Technical Manual, 13th Edition, 1999,
Manufacturer's Directions From Special Antisera.
Authored by: Peggy Schroeder Revised by: