A number of conditions may cause the peripheral white blood cell count reported by an automatic analyzer to be higher than it actually is.


(1) elevated WBC count reported by an automated analyzer

(2) white blood cell count in peripheral blood smear much less than that reported

(3) presence of aggregates in the peripheral blood smear


Possible causes of a pseudoleukocytosis:

(1) cold agglutinin-related aggregates

(2) other reasons for platelet aggregation (finger stick, etc)

(3) inadequate lysis of red blood cells


The diagnosis of pseudoleukocytosis is confirmed if the white blood cell count agrees with the count seen in the peripheral blood smear following an intervention directed to the probable cause. Keeping a specimen warm during collection, handling and testing can prevent cold agglutinins from forming. Recollection of a specimen from a peripheral vein can avoid fingerstick-related platelet aggregates.

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