difference between a 5-part and a 3-part haematology analyser

A 5-part haematology analyser gives the 

i. WBC  absolute and histogram

2. RBC absolute and histogram

3. PLT absolute and histogram

however with an attached WBC differentials and aboslute

A 3-part haematology analyser gives only;

1. WBC absolute and histogram

2. RBC absolute and histogram

3. PLT absolute and histogram

A combination of an HEMOCUE WBC 5-part differential and absolute and the 3-part haematology analyser gives a 5-part system.

It is also less expensive when compared to the 5-part system