CD4+ Count

T-Lymphocyte Measurement

Test Overview

A CD4+ count is a blood test to determine how well the immune system is working in people who have been diagnosed with human immunodeficiency virus (HIV). CD4+ cells are a type of white blood cell. White blood cells are important in fighting infections. CD4+ cells are also called T-lymphocytes, T-cells, or T-helper cells.

HIV infects CD4+ cells. The number of CD4+ cells helps determine whether other infections (opportunistic infections) may occur. The pattern of CD4+ counts over time is more important than any single CD4+ value because the values can change from day to day. The CD4+ pattern over time shows the effect of the virus on the immune system. In people infected with HIV who are not getting treated, CD4+ counts generally decrease as HIV progresses. A low CD4+ count usually indicates a weakened immune system and a higher chance of getting opportunistic infections.

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Author:	Maria G. Essig, MS, ELS	Last Updated: February 17, 2009
Medical Review:	Caroline S. Rhoads, MD - Internal Medicine Peter Shalit, MD, PhD - Internal Medicine
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