Overview
The indirect antiglobulin test (IAT) detects in vitro antibody sensitization: patient plasma/serum is incubated with red cells, then antihuman globulin (AHG) reagent is added to reveal antibody (and/or complement) that bound during incubation.
Classification
| Application | Cells incubated with plasma | Positive result meaning |
|---|---|---|
| Antibody screen | Reagent screening cells | Unexpected antibody likely present |
| Antibody panel | Reagent panel cells | Supports specificity via rule-out logic |
| AHG crossmatch | Donor unit cells | Serologic incompatibility with that unit |
| AHG-phase antigen typing | Reagent typing antisera + patient cells | Antigen present per reagent |
Morphologic Features
Not a cell-morphology topic. Findings are agglutination/hemolysis reactions read after AHG addition following an in vitro incubation step.
Laboratory Characteristics
- Incubation time/temperature/enhancement medium are method-specific, follow manufacturer insert and SOP
- Adequate washing before AHG addition is required in every application
- Add check cells to every AHG-negative tube; agglutination confirms the negative is valid
- Failed check-cell reaction invalidates the result, repeat before reporting
Reference Intervals
No numeric reference interval, results are reported as reactive/nonreactive (with grading conventions per SOP). Method-specific parameters are manufacturer- and institution-defined.
Clinical and Laboratory Significance
The IAT principle underlies the serologic safety net for antibody detection, identification, and AHG-phase crossmatch compatibility before RBC issue, essential to preventing hemolytic transfusion reactions.
Differential Considerations
True negative (validated by check cells) vs falsely negative (inadequate wash or inactive AHG reagent, caught by failed check cells) vs true positive antibody-antigen reaction, distinguished by control performance and repeat testing per SOP.
Comparison Tables
IAT result validity
| Scenario | Validity | Next step mindset |
|---|---|---|
| AHG-negative tube; check cells react | Valid negative | Accept result per SOP |
| AHG-negative tube; check cells fail to react | Invalid result | Repeat testing before reporting |
| AHG-positive crossmatch | Incompatibility | Do not issue; investigate/select alternate unit |
| DAT positive on patient cells (no incubation) | Not an IAT finding | See Direct Antiglobulin Test lesson |
Classification Frameworks
Not applicable, laboratory test procedure, not a WHO disease classification.
Laboratory Notes
- IAT requires incubation; DAT does not, keep the distinction clear
- Check-cell control is mandatory quality practice, not optional
- AHG crossmatch compatibility is one part of the full pretransfusion process
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
Common questions about using this Indirect Antiglobulin Test (IAT) additional test references Medical Laboratory Library reference in Medical Laboratory Science education.
What is the Indirect Antiglobulin Test (IAT) laboratory reference?
Indirect Antiglobulin Test (IAT) is a Additional Test References entry in the LabPedia Medical Laboratory Library, written for Medical Laboratory Science reference lookup.
How should students use this medical laboratory encyclopedia page?
Read the structured sections for quick orientation, then follow related links into Academy lessons or Challenge Center practice when you need teaching or assessment.
Does this page replace laboratory textbooks?
No. It is a concise educational laboratory reference. Use recognized laboratory medicine sources and your institutional procedures for definitive practice decisions.
Where can I find related laboratory tests?
Use related links on this page when present, or browse Laboratory Library discipline catalogues for laboratory tests and interpretation references.
Is this content part of Medical Laboratory Education on LabPedia?
Yes. Library references support Medical Laboratory Education alongside Academy courses, medical laboratory quizzes, and laboratory case studies.
Can reference details vary between laboratories?
Yes. Methods, intervals, and reporting conventions vary. Always confirm details against your laboratory’s current protocols.
How do I return to Library search or categories?
Use breadcrumbs to open the Library hub, discipline catalogues, or other reference collections for continued medical laboratory resource browsing.