Tareq Abadl on CAD: A Practical Guide to Suspicion, Confirmation, and Correction in the Lab
Tareq Abadl, Medical Laboratory Specialist and Director of the Blood Bank at Dr. Abdelkader Al-Mutawakkil Hospital, posted on LinkedIn:
“Cold Agglutinin Disease – What You Should Know
With winter coming, here’s an important lab concept: Cold Agglutinin Disease (CAD).
What Happens?
In this condition, IgM antibodies become active at low temperatures.
Because IgM has 5 arms (pentamer), it can bind to many RBCs at once → causing agglutination/clumping of red blood cells.
How Do You Suspect It in CBC?
You’ll notice something strange:
Hemoglobin (Hb): Usually normal
MCV: Normal
MCH: High
MCHC: High
This unusual pattern should raise suspicion.
The Deciding Test?
Blood Film (Peripheral Smear)
Under the microscope you will typically see:
RBC Agglutination
This confirms the cause of the abnormal indices.
What About Hematocrit?
Using the simple calculation:
Hematocrit ≈ Hb × 3
You will find that the calculated hematocrit looks normal
— another clue pointing to cold agglutination interfering with automated counting.
How to Handle the Sample?
To fix the problem in the lab:
Warm the blood sample at 37°C before running CBC
After warming, results return to normal and reliable
Tip:
In cold weather, it’s a good practice to warm any CBC sample if results look inconsistent.”
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