Saqib Ullah: Why Do Red Blood Cells Autoagglutinate
Saqib Ullah, Medical Laboratory Technologist at Alkhidmat Foundation Pakistan, shared a post on LinkedIn:
“Why Does Autoagglutination Occur?
Autoagglutination is the spontaneous clumping of a person’s own red blood cells (RBCs) without the addition of blood grouping reagents.
It is usually caused by autoantibodies binding to antigens on the surface of RBCs.
Common Causes
1. Cold Autoantibodies (Most Common)
- Usually IgM antibodies.
- React best at temperatures below 37°C.
- Can cause spontaneous RBC agglutination in vitro.
- May interfere with ABO grouping, Rh typing, and crossmatching.
2. Cold Agglutinin Disease (CAD)
- An autoimmune haemolytic anaemia caused by pathogenic cold-reactive autoantibodies.
- May lead to RBC agglutination and haemolysis.
3. Infections Cold autoantibodies may develop transiently following infections such as:
- Mycoplasma pneumoniae
- Epstein–Barr virus (EBV)
4. Lymphoproliferative Disorders Associated with conditions including:
- Chronic Lymphocytic Leukaemia (CLL)
- Waldenström Macroglobulinemia
Why Is It Important in Blood Banking?
Autoagglutination may cause:
- ABO grouping discrepancies
- False-positive Rh typing
- Incompatible crossmatch results
- Difficulty interpreting serologic tests
How Can It Be Resolved?
- Warm the patient’s sample to 37°C before testing.
- Perform warm saline washing of red cells when appropriate.
- Repeat serologic testing using warmed reagents and techniques.
Quick Fact
If red blood cells are already clumped before adding any reagent, always consider autoagglutination before interpreting the test result.”

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