Immunohematology: LabCE Red cell crossmatch techniques

General requirements

- Appropriately labeled speciment - Sample collected within 3 days if patient has been transfused or pregnant. - ABO & Rh determination - Antibody screen - Confirmation of donor unit type - Serologic or electronic crossmatch if eligible.

Electronic crossmatching

- Cannot be used as the sole crossmatch for patients with clinically significant antibodies - Computer validation is time consuming & requires documentation - A change control plan should be used to ensure all steps uncluding training on the new process is documented.

Goals of Method selection

- Enhances the reactivity of clinically significant antibodies --sensitivity. - Reduces the likelihood of false positive results & positives due to insignificant antibodies -- specificity.

Incubation times

- IS for ABO - 15 minutes or longer for albumin - 10-15 minutes for LISS - 15-30 minutes for PEG 30-60 minutes for saline

Polyspecific Antihuman Globulin - IgG and complement

- Requires QC using complement coated cells each day of use - May detect weak reactive comlement binding clicnically significant antibodies.

Cell suspension

- Usually 2 drops of plasma/serum, 2 drops of additive and 1 drop of 3-5% cell suspension For LISS: Proportions of cell/serum(plasma), LISS reagents and cells critical.

What is a crossmatch?

- part of compatibility testing - Attemps to detect incompatibility between patient's serum or plasma & the red cells in the donor unit - May be serological or electronic.

Special/Rare situations

- using an eluate to crossmatch (when the patient has an antibody indentified only in the eluate) - Enzyme treated donor red cells (Inactivates some antigens so could be used in identifying units, but must be used cautiously)

Which of the following crossmatch methods would be the best method of detecting ABO incompatibility?

Immediate spin

If only ABO compatibility is needed, which serologic crossmatch method is most likely to be used?

Immediate spin.

Temperature

36-38 C for detection of clinically significant antibodies

Standard crossmatch methods

Albumin (IAT) LISS (IAT) PEG (IAT) Saline - False + to preservatives/cold Immediate spin - ABO Electronic computer - ABO Gel - Antiglobulin crossmatching Microtiter plate - Antiglobulin crossmatching

Insignificant antibodies

Allo Anti-M, -N, -Lea, -Leb, P1 Auto Anti-I, -I, -H, -IH Anti-A1 Direct agglutination - IS and room temperature.

Significant antibodies

Allo anti-D, -C, -c, -E, -e,K -Jka, -Jkb, -Fya, -Fyb, -S, -s IAT reactive - 37 C

Which of the following reagents is required to confirm the blood type of a donor unit that is labeled Group A Rh negative?

Anti-A, Anti-B, Anti-D

A patient has a previous history of an anti-E. Which of the following crossmatch methods is required?

Antiglobulin. An antiglobulin crossmatch is required. The immediate spin crossmatch would only detect antibodies that react at room temperature/immediate spin. The 37 C incubation readings would detect warm antibodies that do not need the antiglobulin phase to be detected. A warm crossmatch should be avoided as it is prone to false negative results and can make weak clinically significant antibodies nonreactive.

The warm crossmatch should be considered when the patient has a current positive antibody screen and which of the following?

Cold reactive antibodies that are weakly reactive at 37°C and in the antiglobulin phase.

Which of the following organizations does NOT have a specific requirements for using antigen negative blood components if the patient has a clinically significant antibody?

FDA

All accrediting agencies listed in this course require there be a 37° C reading prior to the antiglobulin phase of the antiglobulin crossmatch.

False

The computer (electronic) crossmatch can be the only crossmatch method used when the patient has clinically significant antibodies. True False

False

Validation of the computer crossmatch can be performed by the software vendor using software at the vendor site. True Falses

False

A specimen collected four days previously can be used to crossmatch units for a patient that is currently pregnant. True False

False.

If the gel crossmatch is used there must be a second crossmatch performed that will detect clinically significant antibodies. True False

False.

Which of the following crossmatch methods requires an additional ABO confirmation by another method?

Gel Crossmatch The correct answer is gel. The product instructions for use of the gel card indicates that it does not reliably detect ABO incompatibility. Therefore, another test to confirm ABO compatibility must be performed. An immediate spin crossmatch is generally the test performed as the ABO confirmation test. Neither the LISS antiglobulin or the albumin crossmatches require an additional test.

A small hospital laboratory is evaluating crossmatch methods. The goal is to use the same procedure for all antibody screens, crossmatches and panels. Which of the following would be the best choice?

LISS antiglobulin. The correct answer is LISS antiglobulin because it includes the antiglobulin phase. Enzymes inactivate some antigens while enhancing the reactivity of some clinically insignificant antibodies. Neither the immediate spin or the electronic crossmatch can be used as the only technique for patients with current or history of clinically significant antibodies.

IgG antihuman Globulin

Less likely to have weak false positive reactions

After the last two transfusions, the patient has exhibited hemolysis along with a failure of the transfused red cells to increase the patient's hemoglobin. No antibodies have been identified in the patient's serum/plasma or in an eluate. What techniques could be used to assess compatibility?

Monocyte Monolayer Assay Selecting antigen matched units Invivo Crossmatch

A patient diagnosed with sickle cell anemia is expected to be placed on a protocol that requires frequent partial exchange transfusions. What considerations should be made in crossmatching units for this patient?

Perform antigen typing or molecular testing and transfuse antigen matched red cells

Which of the following is required by the College of American Pathologists for validation of the computer crossmatch?

Validation of all possible anticipated permutations of electronic crossmatching and release of group specific products

Compatibilty testing CFR

Standard operating procedures - 1. Method of collecting & identifying the blood samples 2. Freah recipient serum or plasma samples less than 3 days old for all pretransfusion testing if pregnant or transfused within the previous 3 months 3. Procedures to demonstrate incompatibility between the donor's cell type & the recipient's serum or plasma type 5. Minor crossmatch 6. Expedite transfusion in life-threatening emergencies

Group O red cells must be administered unless there is a previous result or a second specimen for this pretransfusion test: ____.

The CAP and the AABB require that the patient's ABO or (ABO/Rh) must be verified using a second specimen or a historical test result.

An immediate spin crossmatch as been performed and there is a positive reaction. However, the ABO type of the unit and the ABO type of the patient are the same. What is the most likely cause of a false positive reaction?

The patient's serum/plasma has a cold reactive antibody and the sample was just removed from 4º refrigeration.

The FDA does not have regulations concerning the computer crossmatch. True False

True

Positive patient identification is required when pretransfusion testing specimens are collected. True False

True.

A facility is looking at the possibility of using the electronic crossmatch. Which of the following tasks is likely to be the most time consuming in implementing the process?

Validating the computer software

Special crossmatch methods:

Warm-when patient has non-specific reactions Monocyte monolayer assay- serologically compatible blood is unobtainable Invivo- Serologically compatible blood is unobtainable

A technologist is reviewing the patient's panels and observes a cold reactive antibody that occasionally is active at 37°C. Which crossmatch technique should be avoided to prevent unwanted reactions at the antiglobulin phase?

Warm. When the warm crossmatch is used, there is a significant risk of warming away the reactions to clinically significant antibodies. This technique should be used with caution. The warm crossmatch should not be used to avoid unidentified weak reactions at the antiglobulin phase. LISS, gel and albumin crossmatches generally enhance the reactivity of antibodies reactive in the antiglobulin phase.

Antigen matching

used for: patient who will be transfused multiply Who have strong auto antibodies Who are being treated with immunotherapy drugs