Overview
The antibody screen (indirect antiglobulin test performed with reagent screening cells) detects unexpected red-cell antibodies in patient plasma/serum. It is a detection step, not an identification step.
Classification
| Phase | Antibody class favored | Typical significance framing |
|---|---|---|
| Immediate spin | IgM / cold-reactive | Variable, often less clinically significant, confirm per SOP |
| 37 °C incubation | Transitional / method-dependent | Supports subsequent AHG reactivity |
| AHG (post-wash) | IgG / warm-reactive | Most transfusion-relevant phase |
Morphologic Features
Not a cell-morphology topic. Findings are agglutination/hemolysis grades read at defined phases with reagent screening cells.
Laboratory Characteristics
- Screening cells are phenotyped and lot-specific, consult the manufacturer antigram
- Document reactivity and grade at every phase performed
- Run/interpret autocontrol per protocol to help separate alloantibody from autoantibody
- Positive result routes to panel identification; do not report a specificity from the screen alone
Reference Intervals
No numeric reference interval. Screening cell count, enhancement medium, and phase requirements are manufacturer- and institution-specific, verify current SOP and package insert.
Clinical and Laboratory Significance
A positive screen is the gateway to pretransfusion antibody identification and to prenatal alloimmunization risk flagging; a negative screen supports (but does not by itself guarantee) straightforward compatibility.
Differential Considerations
True alloantibody vs autoantibody vs cold agglutinin/rouleaux artifact vs technical error, differentiated using phase pattern, autocontrol, and, when indicated, panel and DAT correlation.
Comparison Tables
Antibody screen interpretation
| Pattern | Likely explanation | Next step mindset |
|---|---|---|
| 1 cell reactive at AHG; autocontrol negative | Probable alloantibody | Panel identification |
| All cells + autocontrol reactive | Autoantibody / high-frequency Ag / technical | Panel + DAT correlation / referral |
| IS-only reactivity; AHG negative | Cold antibody pattern | Document; apply SOP significance rules |
| All screening cells negative | No antibody detected by this panel | Report per policy |
Classification Frameworks
Not applicable, laboratory test procedure, not a WHO disease classification.
Laboratory Notes
- Screen detects; it never identifies a specificity on its own
- Follow method-specific phase and enhancement requirements exactly
- Repeat-screen intervals on transfused/pregnant patients follow institutional policy
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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