Neutrophils are the most abundant class of white blood cells (leukocytes). They are the body’s front line of defence against bacterial infections. The test provides both the number of neutrophils per litre of blood (neutrophil #) and the fraction of total leukocytes they represent (neutrophil ratio). Results must be interpreted in light of clinical observations, other results from the current blood count, and variations in results over time.
A high number and/or ratio of neutrophils (neutrophilia) is found in acute bacterial infections (sometimes viral or fungal), inflammatory diseases (Crohn’s disease, ulcerative colitis, rheumatoid arthritis, etc.), following a glucocorticoid treatment and, more rarely, in a form of leukemia. The death of certain tissues (necrosis) from burns, trauma, major surgery or myocardial infarction, as well as physiological stress or intense exercise, smoking and pregnancy (in the last trimester) will also be accompanied by neutrophilia.
A reduced number and/or ratio of neutrophils (neutropenia) is found in bone marrow disorders (myelodysplastic syndrome, metastasized bone marrow cancer, aplastic anemia), certain autoimmune diseases (lupus, etc.), very severe infections (through exhaustion of reserves) or as a reaction to medications or chemotherapy.