Apheresis

[Sarah]

The dropping of a letter or syllable from the beginning of aword; e. g., cute for acute.

[Tariq Zaki]

In apheresis, blood is removed from a person and then returned after substances are removed from it.
Apheresis can be used to

Obtain healthy blood components from a donor to transfuse to a person with a disorder
Remove harmful substances or excessive numbers of blood cells from the blood of a person with a disorder (termed therapeutic apheresis)

The different components of blood that can be separated include

Red blood cells
Platelets
Plasma
White blood cells

Plasma contains antibodies (immunoglobulins) and clotting factors, which are sometimes separated from plasma.
The two most common types of apheresis that are used to remove harmful substances from blood are

Plasma exchange
Cytapheresis

Cytapheresis may have different names, depending on the type of cell that is removed from the blood.

Plateletpheresis: Platelet removal
Leukapheresis: White blood cell removal

When plasma is separated from the blood, the procedure is called plasmapheresis. Plasmapheresis is often done on blood from healthy donors to obtain plasma for donation or to obtain specific substances such as clotting factors.
Red blood cell exchange also involves apheresis.

[Tariq Zaki]

The loss of a sound or sounds at the beginning of a word, e.g., in the derivation of adder from nadder.