Why get tested? To diagnose an illness affecting your immune system, such as an infection or viral condition, or other diseases that affect your white blood cells, such as leukemias
When to get tested? As part of a complete blood count (CBC), which may be ordered for a variety of reasons
Sample required? A blood sample drawn from a vein in your arm or by a fingerstick (children and adults) or heelstick (infants)
This article was last reviewed on March 4, 2008.
This page was last modified on April 8, 2009.
The review date indicates when the article was last reviewed from beginning to end to ensure that it reflects the most current science. A review may not require any modifications to the article, so the two dates may not always agree.
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