Neutrophilic Segmentation Profile
In the absence of acute infection or significant chronic illness (cancer, liver disease, chronic nephritis), the hypersegmentation of neutrophil white blood cells is considered a biomarker for vitamin B12 and folate deficiency. The neutrophil hypersegmentation can be fairly specific for folate deficiency – the lower the levels of folate, the more segmented the neutrophils become. The relatively short lifespan of a neutrophil (average 5.4 days) allows for a more rapid response to B12 or folate supplementation, and quick follow-up evaluation to supplementation may be of benefit when working up patients with macrocytic anemias or other conditions associated with B-12/folate deficiency.
B-vitamin status may affect cardiovascular risk, diabetes risk, and hormone metabolism. A lack of B-12 and folate may impair the function of the methylation cycle and raise homocysteine levels. Elevated homocysteine is a risk factor for cardiovascular disease, metabolic syndrome (insulin resistance) and type II diabetes. B-12 and folate are also required to the synthesis of S-adenosylmethionine (SAMe), a necessary cofactor for phase II detoxification of estrogen metabolites.
Leukocytes are the “first-line” defense of the innate immune system, and protect the body from bacterial pathogens and are capable of phagocytizing foreign cells, toxins, and viruses. Neutrophils are derived from bone marrow, and if there is a deficiency of either vitamin B-12 or folate (vitamin B-9), then new neutrophils cannot be formed. The existing neutrophils are kept in circulation longer, and the older they get, the more segmented their nucleus becomes. A normal neutrophil has 3-5 lobes; the five-lobed population is normally less than 5% of all neutrophils.
An increase in the segmented neutrophil percentage is used to indicate B-12 and folate status, and may more quickly respond to supplementation than red blood cell-based measurements such as red blood cell size (MCV) or hemoglobin content (MCH). Due to the longer lifespan of the red blood cell, MCH and MCV may take over 120 days to respond to treatment.
