What Happens When a CBC Result Doesn't Make Sense?

 If you've ever had a blood test, you've probably seen CBC (Complete Blood Count) on your lab report.

But what happens when the numbers don't quite make sense?

As an MLT working in hematology for almost 9 years, this is something I deal with regularly. Contrary to what many people think, our job isn't simply to put a blood tube into an analyzer and release whatever numbers come out.

🩸 1. We check the specimen

Before anything else, we consider whether there is a problem with sample integrity.

• Was it collected properly? When was it collected (must be within 24 hours of collection time)?
• Is there enough blood? 
• Is there a clot?

A perfectly functioning analyzer can't produce a reliable result from a poor specimen.

We always consider pre-analytical variables and ask for a re-draw if necessary.

🔬 2. We review the analyzer flags

Hematology analyzers don't just give us numbers. 

They can also flag results that need further investigation. Flags can appear on many parameters such as WBC, Hemoglobin and Platelets.

For example, an unexpectedly low platelet count or an unusual white blood cell pattern may trigger a flag. It would also highlight critically low or high result as the result needs to be called to the ordering physician.

We always ask ourselves: "Does this result actually make sense?"

📊 3. We look at previous results

A patient's history can be very helpful.

If today's hemoglobin is similar to previous results, that's one thing. But if it suddenly drops dramatically, we may need to investigate further.

A change doesn't necessarily mean the result is wrong—it could reflect a real change in the patient's condition.

When in doubt, we would always call the nurse or the doctor who are directly providing care to the patient. We may ask if the patient is bleeding or if they are expecting a critical low hemoglobin/wbc/platelet result.

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So what does an MLT actually do?

It's not simply:

Blood tube → Analyzer → Result

It's more like:

Blood tube → Analyzer → Flags → MLT review → Investigation if needed → Result

That's one of the things I find interesting about hematology.

We're not just generating numbers. We're making sure the numbers make sense before they become part of a patient's medical record.

We want to make sure that we are releasing the correct result: not just random numbers.

So when an MLT rejects a specimen and calls for a re-draw, there are good reasons behind it.