A useful pneumonic to remember is SMILED, which stands for Segmented (neutrophils) and Monocytes Increased, Lymphocytes and Eosinophils Decreased.
What can this indicate
A stress leucogram can be completely normal as part of the stress response. It is caused by endogenous release of Adrenocorticotrophic hormone (ACTH) which causes the release of cortisol from the adrenal cortex - this causes the haematological parameters to change. ACTH and then cortisol release can be triggered by pain, stress or excitement.
A stress leucogram can also be seen in Cushing's Disease (AKA hyperadrenocorticism) where there is a pathological increase in the amount of cortisol released endogenously, or via iatrogenic injection of exogenous corticosteroids.
How does it occur?
The glucocorticoid (whether endogenous or exogenous) causes a variety of affects on blood cells, including margination