This week’s case comes from an 84-year-old male who was referred to the haematology team after routine blood tests showed a markedly raised white cell count. Clinically, he reported several weeks of general fatigue but no acute symptoms. He was otherwise well and presented via his GP.

Full blood count results:

• White cell count: 823 ×10⁹/L (Note: This value exceeded the analyser’s linearity range)
• Red cell count: 2.69 ×10¹²/L
• Haemoglobin: 84–106 g/L (range reflects correction due to WBC interference)
• Haematocrit: 0.306
• MCV: 92.4 fL
• MCH: 31.0 pg
• MCHC: 335 g/L
• RDW: 13.5%
• Platelets: 164 ×10⁹/L
• MPV: 9.2 fL

A few images from the blood film:

Based on the images, the clinical presentation and the FBC results, what do you think the diagnosis may be?

How do you approach any parameter that exceeds analyser linearity?

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