Compatibility Testing - CH. 9 Basics & Applied Concepts of Blood Banking and Transfusion Practices

Overview and Definitions of Compatibility Testing

• Compatibility Testing: This process encompasses all comprehensive steps involved in the identification and testing of a donor unit and the blood of a proposed recipient to ensure a safe transfusion.

• Crossmatching: A critical component of compatibility testing that specifically involves the physical mixing of donor red blood cells (RBCs) with recipient serum or plasma.

  • Incompatibility: Indicated by the presence of agglutination or hemolysis during the procedure.

  • Compatibility: Indicated by the absence of agglutination or hemolysis.

Objectives of Compatibility Testing Procedures

• Define compatibility testing and differentiate it from crossmatching.

• List the specific procedures included in routine compatibility tests and explain the purpose of each step.

• Identify and explain the AABB’s (Association for the Advancement of Blood & Biotherapies) Standards for Blood Banks and Transfusion Services regarding compatibility testing.

• Assign crossmatch-compatible components (whole blood, RBCs, plasma, platelets, and cryoprecipitate) for transfusion based on the patient's ABO type.

• Discuss strategies for providing blood when a fully compatible match cannot be located.

• Recognize and discuss the inherent limitations of crossmatching.

• Describe procedures for handling crossmatching in massive transfusion scenarios.

• Analyze the advantages and issues associated with computer crossmatching.

• Compare and contrast Immediate Spin (IS) and Antihuman Globulin (IAT) crossmatching, including specific requirements for each.

• Explain patient identification elements and their critical importance.

• Explain protocols for typing and screening (T&S) and the Maximum Surgical Blood Order Schedule (MSBOS).

• Understand compatibility testing procedures for infants younger than $4$ months of age.

• Discuss principles governing autologous blood crossmatching.

Serologic Crossmatch Procedures

• Immediate Spin (IS) Crossmatching:

  • Performed when there is no evidence of an antibody in the current sample or in the historical record of the recipient.

  • Procedure: Recipient serum and donor RBC suspension are mixed and immediately centrifuged.

  • Purpose: Fulfills AABB standards for detecting ABO incompatibility.

• Antiglobulin Test (IAT) Crossmatch:

  • Performed if the patient demonstrates a clinically significant antibody in the current sample or has a history of such antigens.

  • Phases: Includes all phases, which are IS, incubation at $37^\circ\text{C}$, and the addition of antihuman globulin (AHG).

  • If the patient possesses an autoantibody, autoadsorbed serum may be utilized for testing.

Computer Crossmatching

• Function: Acts as a final check of ABO compatibility during unit selection, replacing the serologic IS procedure.

• Requirements:

  • The recipient must have no antibodies in the current sample.

  • The recipient must have no history of antibodies.

• Safety Measures: Bar codes are utilized to provide additional layers of safety.

Limitations of Crossmatching

• An acceptable (compatible) crossmatch does not provide an absolute guarantee of a successful transfusion.

• Adverse transfusion reactions may still occur despite a compatible crossmatch.

• A negative antibody screen does not guarantee that the recipient is entirely free of significant antibodies.

• A compatible crossmatch does not guarantee the actual survival of the transfused RBCs in the recipient's circulation.

Pretransfusion Testing and Sample Requirements

• Patient Identification and Labeling:

  • AABB Standards require the use of two independent identifiers for both the patient and the sample information.

• Sample Collection:

  • Samples may consist of plasma or serum.

  • Age of Sample: The limit is $3$ days if the patient has been recently transfused or is currently pregnant.

  • Sample Quality: Hemolyzed samples or samples contaminated with intravenous (IV) fluids are unacceptable and must be re-collected.

• Record Review:

  • Current blood ABO and D typing must be compared with any results performed over the previous $12$ months.

  • Previous records must be consulted for any significant events related to testing or transfusion history.

• Repeat testing of Donor Units:

  • Whole blood and RBC units must be re-typed to confirm ABO labeling accuracy.

  • ABO testing is performed on all units.

  • D testing is performed only on donor units labeled as D-negative.

  • Weak D testing is not required for this confirmatory step.

Compatibility Testing Requirements by Age

• Adults:

  • Required tests include ABO/Rh typing, antibody detection, and crossmatching.

• Infants Younger Than $4$ Months:

  • Initial testing includes ABO and D typing (forward group only).

  • Antibody detection testing is performed using the mother's plasma.

  • Serum testing on the infant is not necessary.

  • If an antibody is identified, antigen-negative units must be provided.

Selection of Blood Units

• D-Type Selection:

  • D-negative units should be administered to D-negative recipients, with particular emphasis on women of child-bearing age.

  • If an anti-D antibody has formed, antigen-negative blood is mandatory.

• Antigen-Negative Recommendations: Recommended for the following antibodies:

  • ABO

  • Rh

  • Kell

  • Duffy

  • Kidd

  • Others if they react at the AHG phase.

Components of a Blood Product Label

• Donation Identification Number: Barcode and eye-readable number of the component or pool.

• Collection Date: The date of donation or preparation for pooled components (e.g., $04 \text{ May } 2018$).

• Expiry Date and Time: Barcode and eye-readable (e.g., $15 \text{ Jun } 2018 \text{ } 23:59$).

• Component Description: Proper name (e.g., RED CELLS in SAG-M, Leucocyte Depleted), code ($04390$), and details like anticoagulant/additives.

• Storage Conditions: Required temperature range (e.g., Store at $+2^\circ\text{C}$ to $+6^\circ\text{C}$).

• Volume: (e.g., Volume: $258 \, \text{ml}$).

• ABO and RhD Group: Both barcode and eye-readable text (e.g., Rh D NEGATIVE).

• Special Test Results: Area for red cell, platelet, and HLA phenotype/genotype (e.g., CMV Negative, $rr \text{ C- E- c+ e+}$).

• Modifier Area: Lists attributes not in the component code.

• Manufacturing Cost: Indicative cost (e.g., Manufacturing cost $\$412.66$).

• Warnings and Instructions:

  • Properly identify intended recipient.

  • Do not use if contents show visible signs of deterioration.

  • Infectious disease statement: "Donation tested and non-reactive for specified markers for HIV 1&2, hepatitis B&C, HTLV and syphilis."

Issuing and Reissuing Blood Products

• Issuance Requirements:

  • Physician’s order is mandatory.

  • Verification of intended recipient’s two independent identifiers, ABO group, and D type.

  • Requisition form comparison: Verification of patient name, unique ID, and blood product.

  • Check donor unit tag against the requisition form and the blood product label.

  • Check expiration date and perform a visual check for discoloration, clots, or abnormal appearance.

  • Documentation: Must include the person issuing and the person receiving the unit, date, time, and destination.

• Reissue Conditions: Blood products may be reissued only if:

  • The product has not been entered (the container remains sealed).

  • The unit has been maintained between required temperature conditions ($1^\circ\text{C}$ to $10^\circ\text{C}$ for RBCs).

  • The unit has not expired.

  • The return is fully documented (who returned it, time, temperature, and satisfactory inspection results).

Emergency and Massive Transfusion Protocols

• Emergency Release:

  • Must be signed by a physician.

  • Donor unit tag must indicate "Emergency Release" and state that compatibility or infectious disease testing is incomplete.

  • Maintain patient identifiers and donor unit numbers.

  • Segregate and retain segments from units for retrospective crossmatching.

• Massive Transfusion:

  • Defined as a total volume blood exchange within a $24$-hour period.

  • Emergency Protocol: Group O, D-negative units are administered.

  • If D-negative is unavailable, Group O, D-positive blood may be given to D-negative individuals who are not of child-bearing age.

  • Once the recipient's blood group is established, ABO-identical units should be used.

Surgical Blood Management Protocols

• Maximum Surgical Blood Order Schedule (MSBOS):

  • Determined by facility physicians and the Blood Bank medical director based on average blood usage for specific procedures.

  • Acts as a standard for surgical blood orders to improve utilization.

• Type and Screen (T&S) Requests:

  • No alloantibodies detected: No further testing required. Perform IS or computer crossmatch if units are ordered.

  • Alloantibody detected: Identify the antibody. Perform a complete crossmatch (IS and AHG) on units that are antigen-negative for that antibody. Rule out or identify additional antibodies.

  • Record of previous alloantibody: Perform IS and AHG (antiglobulin) crossmatch on units that are antigen-negative for both the prior and any newly identified alloantibodies.

Special Circumstances and Non-RBC Products

• Autologous Blood: Procedures must ensure units are correctly located and transfused to the intended recipient. Tracking is monitored manually or via computer.

• Non-RBC Products:

  • Frozen Plasma, Platelet Concentrates, and Cryoprecipitate: Generally do not require a crossmatch.

  • Plasma compatibility: Should be ABO serum compatible with the recipient.

  • Platelets and Cryoprecipitate: May not strictly need to be ABO compatible.

  • Apheresis Platelets and Granulocyte Concentrates: May require crossmatching if they contain more than $2 \, \text{mL}$ of RBCs.