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Identifying Antibodies. The Antibody Panel. CLS 422 Clinical Immunohematology I. Objectives. Discuss clinical situations when it is appropriate to perform antibody identification. Define a panel of cells. Explain how the following factors aid in the interpretation of antibody panels:

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identifying antibodies

Identifying Antibodies

The Antibody Panel

CLS 422

Clinical Immunohematology I

objectives
Objectives
  • Discuss clinical situations when it is appropriate to perform antibody identification.
  • Define a panel of cells.
  • Explain how the following factors aid in the interpretation of antibody panels:

a. Cross-out technique

b. Variation in strengths of reaction

c. Phases of reaction

d. Autocontrol

e. Red blood cell antigen typing

objectives1
Objectives
  • List testing that can be performed to confirm the identification of antibodies.
  • Identify the antibodies present, when given panel results.
when is an antibody identification panel performed

When is an antibody identification panel performed?

When the antibody screen is positive.

when to perform test
When to perform test
  • The panel red blood cells (RBCs) are tested against the patient’s serum or plasma in order to identify the unexpected antibody or antibodies present.
identification
Identification
  • Antibody screen – positive
  • Run antibody panel to identify antibody (-ies).
  • If original panel does not provide a clear-cut ID, test additional RBCs.
    • Selected cells
    • Alternate methods
confirmation
Confirmation
  • Rule of 3 and 3
  • Antigen type patient’s RBCs.
    • Landsteiner’s Law!!!
the panel
The Panel
  • Series of 8 to 20 Group O RBCs
    • Various distribution of the most common RBC antigens
    • Suspended in a preservative to protect antigen integrity for 2 -4 weeks
    • Packaged with a lot-specific antigram
auto control
Auto Control
  • Patient’s serum/plasma tested against a suspension of patient’s RBCs
    • Optional
    • Evaluate results in conjunction with patient history
      • Autoantibody
      • Newly forming alloantibody
    • If patient has a positive DAT, auto control will be positive
test method
Test Method
  • Usually the same as was used for the antibody screen
  • Must include incubation at 37oC
  • Must include an AHG phase with reagent containing anti-IgG
exclusion
Exclusion
  • Begin with the RBCs that failed to react
  • The antibody in the serum is not directed against the antigens on these RBCs, so we can eliminated these antibody specificities
  • Look at alleles to avoid problems with dosage!
    • Exclusion should be done using RBCs having homozygous antigen expression.
    • Exceptions are low prevalence antigens
inclusion
Inclusion
  • Of the antibody specificities that have not been excluded, match the pattern of positive and negative reactions with the pattern of antigen positive and antigen negative cells.
  • There must be an explanation for each positive reaction seen.
other points to consider
Other Points to Consider
  • In what phase(s) of testing is the antibody reactive?
    • May give clue as to antibody identity and clinical significance.
  • Is the strength of reaction the same for each cell that reacts, or is there variation in strength?
    • Dosage, antigen variability, or multiple antibodies.
  • Is the antibody reacting only with “homozygous” cells of a certain specificity?
    • Weak antibody showing dosage.
  • Did the autologous control react?
    • Autoantibody or newly forming alloantibody.
probability
Probability
  • Rule of 3 and 3
  • For each antibody specificity, are there 3 antigen positive cells that reacted and 3 antigen negative cells that did not react?
    • May use screen cells in addition to panel cells to fill this rule
    • Cells do not need to have homozygous antigen expression to fill this rule
antigen typing
Antigen Typing
  • Confirms the antibody identification
    • LANDSTEINER’S LAW
  • Test patient’s RBCs (unknown antigen) against appropriate anti-sera (known antibody)
  • Results should be
    • negative
  • Run positive and negative controls for anti-sera
  • A positive DAT or recent transfusion may invalidate the typing results
value of patient history
Value of Patient History
  • The following additional information may assist in determining the identity of the antibody:
    • History of antibodies
    • Transfusion, transplant, pregnancy (how many and how long ago)
    • Medications
    • Diagnosis
    • Ethnicity
reporting
Reporting
  • Panel results are reported as “anti-” and then the specificity
    • Anti-K
  • If specificity cannot be determined at this point, additional testing must be performed