Principle: | Antigram Interpretation: | Results Derivation: | References:
Identification of the antibody present in the plasma/serum may be made by matching the reactions obtained in an antibody identification procedure with the antigram antigen profile furnished with the reagent red cells. For example, if the plasma/serum reacts with the Rh(D) positive cells but not the Rh(D) negative cells, the antibody is probably Anti-D.
II. Antigram Interpretation:
Note: More than one alloantibody may be present in the patient's plasma/serum. Watch for “masking” of one antibody by another antibody’s reaction pattern.
1. Locate the first cell that gives a negative reaction. Start at one end of the antigram and cross out each antigen that is present on that particular cell. Use an “X” for homozygous cells and a “/” for heterozygous cells.
Note: If the negative reacting panel cell is heterozygous for certain antigens, (i.e.: Jka+/Jkb+; or there is only one negative cell for a common antigen) that antigen has not been eliminated on the basis of this cell. This dosage effect can give false negative reactions due to the weakened antigenic expression. Further investigation is indicated.
2. Continue crossing out additional antigens by repeating this procedure for each negative reacting panel cell.
3. When the original panel yields more than one possible antibody or only one cell is negative for a common antigen, it may be necessary to react the patient's plasma/serum with other cells from alternate panels. Choose cells that are negative for the primary antigen, but are positive for the antigen to be ruled out. For example: the patient's reaction pattern matched Fya, but we cannot rule out Kell. Test the patient's plasma/serum with cells that are negative for Fya but positive for the Kell antigen. A negative test result in the appropriate phase will rule out the Kell, but a positive reaction confirms it.
A. Select cells from Panel B or an expired Panel A or Panel B. Make sure that any panel cells selected from different panels do not have the same donor ID numbers as cells already tested.
B. Test the patient's plasma/serum with these selected cells at the reactive phase. Record results on the appropriate panel antigram and attach it to the original work.
C. Note the Q.C. requirements for outdated panels. (Refer to the “Blood Bank Reagents; Quality Control” procedure.)
4. Once the antibody(ies) is(are) identified, the patient and prospective donor cells must be typed for the corresponding antigen(s). Refer to “Antigen Typing” protocol.
5. Always consult a pathologist when an antibody identification is performed. It will be the decision of the pathologist to release blood for transfusion. A pathologist must initial and date the panel antigram used for the antibody identification.
6. Unresolved problems are referred to the Mississippi Valley Regional Blood Center (MVRBC) in Davenport, IA after consultation with a pathologist.
III. Results Derivation:
1. Autologous Control:
It is important to know how the patient's own plasma/serum and cells react in vitro to evaluate whether alloantibody, autoantibody or both are present. Plasma/serum that agglutinates ONLY reagent cells USUALLY contains alloantibody(ies). Simultaneous reactivity with the autologous cells must be interpreted carefully. Alloantibody reacting with circulating donor cells can easily be misinterpreted as an autoantibody.
2. Single antibodies:
These are characterized by the observation of straightforward positive and negative reactions that fit the pattern of one of the antigens in the panel antigram. Some problems encountered with single antibodies are:
A. Not all cells positive for a particular antigen react with the plasma/serum, or the strength varies:
a. Dosage: heterozygous vs. homozygous cells.
b. Variation in antigenic strength among various donors or reagent cells.
B The antibody may be reacting in an unexpected manner:
a. An antibody reacts at 37°C, which ordinarily is expected to react at room temperature.
b. A weak antibody may only react with homozygous cells.
C. The antibody reacts with an antigen not listed on the panel antigram. Refer to the extended antigen profile for the red cells that are positive to get additional antigen information.
D. Agglutination of all cells due to an antibody directed against a high frequency or public antigen.
E. Only one screening cell or donor cell is positive and no reactions are seen in the panel.
a. There may be an antibody to a low frequency or private antigen.
b. The titer may be too low to identify.
3. Multiple Antibodies:
When a plasma/serum contains two or more antibodies, identification may be difficult. These problems are usually demonstrated in one of the following ways:
A. The reaction pattern of the plasma/serum does not fit that of a single antibody.
B. Reactions of varying strength are observed with the panel cells, and/or the plasma/serum reacts with different panel cells in a pattern that cannot be explained on the basis of dosage.
C. Unexpected agglutination is observed when testing plasma/serum with a presumed single antibody against cells known to be negative for that antigen.
4. Unresolved problems are usually referred to MVRBC at Davenport, IA after consultation with a pathologist.
1. American Association of Blood Banks, “AABB Technical Manual”; current edition.
2. Reagent Red Blood Cells Resolve Panel A, Ortho-Clinical Diagnostics; package insert, current version.
3. Reagent Red Blood Cells Resolve Panel B, Ortho-Clinical Diagnostics; package insert, current version.
i. June 2003 S. Rodriguez/N. Combs
September 2009 S. Rodriguez (no changes)
November 2010 N. Combs (Revised: II.1., 3.C., 6.; III.2.C., E.b., 3.,4.)