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Factors affecting the results or processing of blood counts

Here are some of the factors which could affect the results or processing of blood counts. This is not an exhaustive list. There may be other factors affecting the reporting of results which are not listed. Also see a list of factors affecting all sections of the haematology department.


Test Factors affecting result/processing Outcome


Small sample

Paediatric - would process if there is greater that 100ul. Otherwise comment 'Insufficient'

Adult - would process if blood volume is sufficient to reach the bottom of the label- otherwise comment 'Insufficient'


Small sample

Paediatric - separate sample ESR.

FBC + ESR requires 2ml in FBC tube otherwise will be reported as 'Insufficient'

FBC and Film

Old sample (greater than 48 hours)

FBC would not be processed and comment - 'Too old for analysis'

Film would be reported as - 'Too old for morphology'
FBC, ESR and Retic Clotted sample Would not be processed


EDTA may cause clumping of platelets

This would result in a falsely low platelet count - laboratory will check a blood film and ask for citrated (Coag) sample to attempt an accurate measurement of the platelets


Contaminated with red cells

Would process - appropriate comment will be added
Bone marrow smears Not enough marrow material to perform stains on Could not perform stains - repeats would be requested