What it measures
A drop of blood is spread thinly on a glass slide, stained and looked at under a microscope by a lab scientist or haematologist. They describe the size, shape and look of the red cells, white cells and platelets. It shows changes that counting machines cannot.
Why people test it
- Requested when a full blood count shows results that need a closer look.
- Used to look at red cell shapes in anaemia, and at unusual white cells.
- Used to look for some infections of the blood, such as malaria.
Typical range
There is no number or range. The lab reports in words, saying either that no abnormality was seen or naming the changes found in the cells.
Finger-prick or vein?
A vein sample is usually advised. The slide is best made from fresh blood that has not clotted, as cells change shape in older or clotted samples.