Skip to main content

SOP

Indirect Antiglobulin Test (IAT / Indirect Coombs)

SOP for detecting in vitro sensitization of RBCs by patient serum antibodies.

Last verified 1 month ago 1 min read Blood Bank / Transfusion Medicine Immunohematology #blood bank #iat #indirect coombs #antibody screen
Link copied!
Document Control
Version
1.0
Effective
Aug 28, 2026
Reviewed
Aug 29, 2026
Department
Blood Bank / Transfusion Medicine
Principle

Patient serum is incubated with reagent RBCs at 37°C to allow antibody binding (sensitization). After washing, AHG is added to cross-link the bound antibodies, causing agglutination.

Standard Operating Procedure: Indirect Antiglobulin Test (IAT)

1. Purpose: Detect unexpected antibodies in patient serum (e.g., pre-transfusion testing, prenatal screening).

2. Specimen: Patient serum or plasma; reagent screening/panel RBCs.

3. Reagents: LISS or PEG enhancement media, 37°C incubator, polyspecific AHG, check cells.

4. Procedure:

  • Add 2 drops patient serum to tube with 1 drop reagent RBCs.
  • Add enhancement media (if required).
  • Incubate at 37°C for 15-30 minutes.
  • Wash 3-4 times with saline.
  • Add 2 drops AHG, mix, centrifuge, and read.
  • Add check cells to negative reactions.

5. Interpretation: Agglutination = Positive IAT (antibody present). No agglutination + check cell reaction = Negative IAT.

Frequently Asked Questions

They enhance antibody uptake by RBCs, reducing incubation time and increasing test sensitivity.