Key Takeaways

Leukocytosis is defined as a total white blood cell count (WBC) > 11 x 109/L..

Neutrophilia is defined as an absolute neutrophil count > 7.7 x 109/L.

Neutrophilia may be reactive or clonal.

Causes of reactive neutrophilia include infection, inflammation, smoking, metabolic syndrome, solid tumor, medication, stress and splenectomy.

A causal role of smoking in neutrophilia is supported by a dose-response relationship, with a larger effect seen in heavier smokers, as well as the fact that smokers’ higher WBC counts reverse rapidly after smoking cessation (typically within 8 weeks).

Diagnosis is supported by normalization of counts upon smoking cessation.

Smoking is associated with mild elevation of white cell count. If the white cell count/neutrophil count are greatly increased, other causes should be sought.

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