Overview
The major crossmatch is the laboratory step that tests patient plasma against a specific donor unit's red cells before that unit may be released. It is performed by one of three methods, electronic, immediate spin, or antiglobulin (AHG), selected according to the patient's antibody screen result and antibody history.
Classification
| Method | Detection scope | Typical eligibility (institution-defined) |
|---|---|---|
| Electronic (computer) | ABO compatibility via validated logic | Two concordant ABO determinations, negative screen, no significant antibody history |
| Immediate spin | ABO compatibility via serologic room-temperature reaction | Negative screen, no significant antibody history, not electronic-eligible |
| Antiglobulin (AHG) | ABO compatibility plus IgG-mediated incompatibility | Positive screen or history of a clinically significant antibody |
Morphologic Features
Not a cell-morphology topic. Findings are compatible/incompatible outcomes, agglutination or hemolysis on serologic methods, or a passed/failed validated logic check on the electronic method.
Laboratory Characteristics
- Crossmatch is unit-specific, a separate compatibility outcome is required per donor unit
- Method eligibility is determined by antibody screen result and antibody history, verified before method selection
- A compatible result from an ineligible method is not a valid compatibility determination
- Incompatible results on any method are documented and investigated before an alternate unit is selected
Reference Intervals
No numeric reference interval. Outcomes are reported as compatible or incompatible per unit. Exact eligibility criteria for each method are institution- and regulation-specific, verify current SOP.
Clinical and Laboratory Significance
The crossmatch is the final laboratory safeguard confirming that a specific donor unit is compatible with a specific patient before issue, catching ABO incompatibility on all three methods and IgG-mediated incompatibility specifically on the AHG-phase method.
Differential Considerations
Not applicable in the disease sense. The relevant distinction is between a valid compatible result (correct method for that patient's eligibility profile) and an invalid or incompatible result requiring investigation, method escalation, or unit substitution.
Comparison Tables
Crossmatch method selection
| Patient profile | Appropriate method category | Rationale |
|---|---|---|
| Concordant type, negative screen, no antibody history, electronic-eligible | Electronic crossmatch | ABO logic check sufficient per eligibility criteria |
| Negative screen, no antibody history, not electronic-eligible | Immediate spin crossmatch | Serologic ABO check without AHG phase |
| Positive screen or antibody history | AHG crossmatch | Only method scope here designed to catch IgG-mediated incompatibility |
| Incompatible result at any method | Hold unit; investigate | Do not release without resolution |
Classification Frameworks
Not applicable, laboratory test procedure, not a WHO disease classification.
Laboratory Notes
- Method choice follows screen and history, confirm both before selecting a method
- Crossmatch outcomes are recorded per unit, not per patient in aggregate
- See the Electronic Crossmatch and Immediate Spin Crossmatch entries for method-specific procedure and eligibility detail
References
Authoritative textbooks, guidelines, and reviews supporting this reference entry. Verify reference intervals, critical limits, and reflex criteria against institutional protocols and current guideline editions.
Textbooks
- Cohn CS, Delaney M, Johnson ST, Katz LM, eds. Technical Manual. 21st ed. AABB; 2023.
- Harmening DM. Modern Blood Banking & Transfusion Practices. 7th ed. F.A. Davis; 2019.
- McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Elsevier; 2021.
CLSI and Professional Guidelines
- AABB. Standards for Blood Banks and Transfusion Services (verify current edition and institutional adoption).
- Clinical and Laboratory Standards Institute. Related immunohematology and specimen identity standards (verify current documents and institutional adoption).
Frequently Asked Questions
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