White blood cell (WBC) counts are indicative of the immune status of your child. Total white blood cell counts are similar for children and adults; however, newborns have greatly raised WBC ranges, which typically approach normal adult levels, about two weeks after birth. WBC counts are normally part of a complete blood count (CBC) that a physician may order if your child is feeling unwell.
White blood cells (WBCs) are one component of blood along with red blood cells, platelets and plasma. WBCs are primarily responsible for responding to infections of all types. Because they need to response to a wide range of infections, and potentially for a long time, there are different types of WBCs as well. A WBC count will detect all white blood cells as well as provide a breakdown of WBC types from a single blood draw.
For most children, as well as adults, the normal range of total WBCs is 4,500 to 11,000 WBCs per microliter. This number is elevated in newborns, up to 9,000 to 30,000 WBCs per microliter, but this number should fall to the adult level after about two weeks of life. Total WBC count normally rises when your child has an infection, but can also rise in other medical situations as well, such as leukemia. Low WBC counts can indicate an increased susceptibility to infection.
There are multiple types of WBCs, and the percentage of total WBCs that each subtype makes up changes as children age. The types of WBCs that are detected during a normal lab test are neutrophils, lymphocytes, monocytes, eosinophils and basophils. Neutrophils and lymphocytes are the most abundant WBCs. Children normally have more lymphocytes than neutrophils, though this predominance switches to primarily neutrophils after about eight years old.
The WBC count is a blood analysis test; therefore, blood needs to be drawn from your child. In older children, blood will typically be drawn from the an arm vein using a needle, as is done for adults. In younger children or newborns, however, a lancet or finger prick can be used to obtain enough blood to perform the test. The WBC count is often part of a complete blood count, which will quantify all the components of blood in one test.
The WBC count accurately reflects the immune health of your child. Elevations typically represent infections, while decreases indicate increased infection risk. The breakdown of types of WBCs can help your pediatrician determine what type of infection your child has, as different types of WBCs increase in number to different types of infections. WBC counts can also be used to monitor recovery from illness for more severe cases.