This week’s case featured an 84-year-old male referred after routine blood tests showed an extremely elevated white cell count. He reported increasing fatigue but no other significant symptoms.
Summary of key findings:
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WBC: 823 ×10⁹/L
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Exceeded analyser linearity → dilution required for accurate quantitation
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RBC: 2.69 ×10¹²/L
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Hb: 84–106 g/L (corrected for WBC interference)
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Platelets: 164 ×10⁹/L
Blood film features:
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A pleomorphic population of lymphocytes
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Small to medium-sized cells with a high nuclear-cytoplasmic ratio
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Clumped (“soccer-ball”) chromatin
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Occasional prolymphocytes
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Presence of smear cells
These features are classical for CLL. The combination of a markedly elevated lymphocyte count, characteristic morphology, and a supporting clinical picture strongly points to chronic lymphocytic leukaemia as the final diagnosis.
Dealing with results outside the analyser linearity range:
This case also raised an interesting challenge from an analytical perspective. How do we deal with results that are outside the linearity range of an analyser? Best practice includes:
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Performing a manual or automated dilution of the sample using the analyser’s recommended protocol
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Repeating the test on the diluted specimen to obtain a reliable, linear result (remember to multiply the diluted result by the dilution factor to get the actual result!)
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Documenting the action including the dilution factor
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Correcting impacted parameters, such as haemoglobin (WBC interference), if required
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Reviewing histograms/scatterplots for flagging patterns that may require additional checks