Blood Smear

... Why get tested?
To help evaluate how “normal” and mature red blood cells, white blood cells and platelets are. To distinguish between different types of white blood cells and to determine their relative percentages in the blood. To help diagnose a range of deficiencies, diseases and disorders involving blood cell production, function, and destruction. To monitor cell production and cell maturity in diseases such as leukemia.

When to get tested?
When a CBC and Differential indicates the suspicion of abnormal or immature cells. When a doctor suspects a deficiency, disease or disorder that is affecting blood cell production. When you are being treated or monitored for a blood cell related disease.

Sample required?
A blood sample drawn from a vein in your arm or by pricking a finger, ear, or -- in the case of an infant -- a heel.
...