A differential count blood test is one of the routine tests that is performed to know the overall health of the body. It may be the part of complete blood test, or it may be conducted separately in the case there are some health issues such as blood infection. It is performed on the white blood cells of our blood to know the blood counts of different types of WBCs present in our body. The main components of the DC blood test are neutrophil, lymphocyte, monocyte, eosinophil and basophil. These cells are checked when there is any abnormality, infection, or immune system disorder.