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Identifying Antibodies

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

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  1. Identifying Antibodies The Antibody Panel CLS 422 Clinical Immunohematology I

  2. 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

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

  4. When is an antibody identification panel performed? When the antibody screen is positive.

  5. 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.

  6. 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

  7. Confirmation • Rule of 3 and 3 • Antigen type patient’s RBCs. • Landsteiner’s Law!!!

  8. 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

  9. Antigram

  10. Panel Antigram

  11. 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

  12. 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

  13. Interpreting Panel Results

  14. 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

  15. Exclusion

  16. 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.

  17. Inclusion

  18. 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.

  19. 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

  20. The Rule of 3 and 3

  21. 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

  22. Selecting Controls for Antigen Typing

  23. 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

  24. 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

  25. The End

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