Low lymphocytes may be caused by chemotherapy, leukemia, radiation therapy or sepsis, and high neutrophils may be caused by stress, infection, gout or rheumatoid arthritis, according to MedlinePlus. Both lymphocytes and neutrophils are types of white blood cells and are collected in a blood differential test.
A blood differential test, where lymphocytes and neutrophils are counted, is usually done to test for an infection, leukemia or anemia, explains MedlinePlus. In this type of test, an increase in one type of white blood cell may cause the decrease of another. High levels of any white blood cell may be attributed to inflammation or an immune response.
There is very little risk to this test, as it is done by taking blood from an individual, claims MedlinePlus. Since the veins and arteries vary in size, some people may have a more difficult time having blood taken than others. Some of the side effects that are rare, but possible, include excessive bleeding, fainting and blood accumulating under the skin. It is also possible, since the skin is broken, that an infection could set in. There is no preparation necessary for this test, and it is relatively painless. Some patients report throbbing around the injection site following the blood differential test.