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CD4 count
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The CD4 count is a lab test that does one thing: count how many CD4 T lymphocytes you have. They are a type of lymphocyte, and they are named for a piece that sticks out from their surface, the CD4 receptor.
Counting them one by one under a microscope would be impossible, so the standard method is flow cytometry. First, antibodies tagged with a fluorescent label and designed to bind only to that CD4 receptor are added. The cells that end up labeled glow, and the machine counts them as they go by. It is like marking only one team with glow-in-the-dark paint and then counting the ones that light up as they pass through a doorway.
Normal is between 500 and 1,500 cells per cubic millimeter of blood. The CDC, the public health authority in the United States, uses a count below 200 as one of the criteria for diagnosing AIDS.
The number is not fixed over the course of the day. It tends to be lower in the morning and climb as the hours pass.
In brief
The CD4 count is the lab test that measures how many CD4 T lymphocytes you have.
A census of a single cell population.
The standard method is flow cytometry: fluorescent antibodies bind to the CD4 receptor and the machine counts the labeled cells.
The normal range runs from 500 to 1,500 cells per cubic millimeter.
The CDC uses a count below 200 as a criterion for AIDS.
The number swings during the day: it tends to be lower in the morning and rise as the hours pass.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingCD4 Cell Count and HIV, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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