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Sep 21, 2026, 12:15

Kholoud Al Busaidi: Cold Agglutination and Its Impact on CBC and Blood Grouping Results

Kholoud Al Busaidi, Medical Laboratory Intern at Ministry of Health Oman, shared a post on LinkedIn:

“Had a patient with visible RBC clumping in the EDTA sample. That raised the possibility of cold agglutination, potentially related to cold-reactive IgM antibodies.

The first CBC results were clearly questionable. An extremely high MCHC combined with a low RBC count and HCT was a major red flag.

Then the blood group came back as AB positive, while the patient’s previous record showed O positive. That discrepancy needed to be investigated.

So I warmed the EDTA sample at 37 degree C for 30 minutes and repeated the CBC. The results came back much more consistent.

For the blood grouping, the red cells were washed with normal saline, and the ABO Rh typing was repeated.

The result was O positive, matching the patient’s previous record.

Now, this doesn’t mean we’re making a clinical diagnosis of cold agglutination. From the laboratory side, the findings were suggestive of possible cold agglutination and, more importantly, showed potential analytical interference.

Cold agglutination can interfere with automated CBC parameters, particularly RBC count, HCT, MCV, MCH, and MCHC.

So when the numbers don’t make sense, you don’t force them to make sense.” Kholoud Al Busaidi: Cold Agglutination and Its Impact on CBC and Blood Grouping Results