Q: I had a routine blood test, and my doctor told me my white blood cell count was low. Should I be worried?

Q: I had a routine blood test, and my doctor told me my white blood cell count was low. Should I be worried?


A: Several different types of white blood cells fight bacterial, fungal, viral and/or parasitic infections, as well as serving other functions. In adults, a white blood cell count less than 3,500 cells per microliter is considered low; the normal threshold in children varies with age.


White blood cells are made in the bone marrow and are released into the blood stream. They then circulate in the blood stream or take up residence in the vascular endothelium system or certain body tissues/organs. Old white blood cells are cleared from the blood stream by the spleen and liver.


The white blood cell count is measured by evaluating the concentration of white blood cells in the bloodstream. Falsely low measurements can occur due to clumping of the white blood cells or from other factors.


A truly low white blood cell count can be from a congenital cause or it can be acquired. There are many different congenital conditions that cause low white blood cell counts. An acquired low white blood cell count can be due to:




Decreased bone marrow production: This may be due to infections (viral infections are the most common cause), medication reactions (the second most common cause), certain congenital conditions, medication effects (such as from chemotherapy agents) or from cancer/infections/other conditions that infiltrate the bone marrow "crowding out' its ability to produce normal white blood cells. In addition, certain autoimmune conditions can affect the hormones that trigger white blood cell production, hence "turning off the switch" that tells the bone marrow to produce white blood cells. There are also many conditions that may directly affect the cells that make the white blood cells, causing ineffective production of normally functioning cells. High thyroid levels and/or certain vitamin or mineral deficiencies (such as B-12 or folate deficiencies) can cause inadequate white blood cell production as well.

Increased destruction of white blood cells in the bloodstream: This may be due to autoimmune conditions (possibly triggered by medication reactions) or many other conditions.

Increased clearance of white blood cells (even normally functioning ones): This may be due to an enlarged spleen (from whatever cause).

Using them up faster than they can be replaced: Overwhelming infections can do this.

Migration of the cells out of the bloodstream: In some conditions white blood cells can migrate to the vascular endothelium or other tissue pools/organs.

The type, risk and severity of any clinical problem from low white blood cells depends on the type of white blood cells that are affected and how severe the deficit is. Many of the conditions that cause a low white blood cell count are benign, causing minimal or no clinical problems. However, since white blood cells are one of the main ways the body fights infections, a low white blood cell count can lead to an increased risk of infection.


Polymorphonuclear cells (PMNs) are the most common type of white blood cells and, hence, low white blood cells almost always implies a low PMN count. Since PMNs fight bacterial infections, overall this is the most common infection from low white blood cells.


Low white blood cell count is more common in African Americans; 5 percent to 10 percent of black Americans have low neutrophil counts, as opposed to less than 1 percent of white Americans. Thankfully, this is usually due to a benign inherited condition, so most of these patients do not have clinical problems.


In patients with a mildly decreased white blood cell count noted on a routine blood test who do not have a history of infections, other testing may not be required. However, in patients with a history of infections, or those with other concerning results of their blood test, other testing may be indicated.


For example, if transient neutropenia is suspected (a condition where a patient's PMNs drop for several days every few weeks, predisposing them to infection) blood tests to check their white blood cell count may be required several times per week for several weeks. If decreased cell production is suspected, a bone marrow biopsy may be required. If an autoimmune condition is suspected screening tests for a collagen vascular disease or other testing may be needed. If a chronic infection is suspected -- for example, HIV infection -- other tests may be indicated.


Many patients with low white blood cells do not require treatment. However, good dental care (since this can be a source of infection) and increased vigilance when they have a fever or appear ill is indicated.


Depending on the cause of the low white blood cells, some patients may benefit from antibiotics to minimize their risk of acquiring an infection. For example, certain HIV patients are put on specific types of antibiotics.


For some patients -- like those receiving chemotherapy for certain cancers -- medications that stimulate the bone marrow to increase production of white blood cells may be beneficial.


A low white blood cell count should trigger a discussion with your health care provider. He or she can evaluate your history and risk factors, as well as the other details of the test results, and determine what other testing and/or treatments may be required.


Jeff Hersh, Ph.D., M.D., F.A.A.P., F.A.C.P., F.A.A.E.P., can be reached at DrHersh@juno.com.


MetroWest (Mass.) Daily News