CD4 T-Cell Count and what is means
The CD4 T-Cell count (sometimes known as CD4 count) is an indicator of the immune function in patients who are infected with HIV.
For users reading this who are not infected with HIV please note that it is NOT used in diagnosing a HIV infection.
So by measuring a person’s CD4 count, we get an idea of how healthy his immune system is. In a person who is infected with HIV, the HIV virus infects and kills CD4 cells. As more and more CD4 cells die, a person’s immune system gets weaker and weaker until he/she develops AIDS. If no treatment is given, he/she will die from an infection that the weakened immune system just cannot fight off.
So measuring the CD4 count in a person with HIV is very important for several reasons:
- Determining the urgency of starting ART
- Deciding if there is a need to prescribe medicines to prevent opportunistic infections
- As a way to see if a person is responding to the ART
Let’s look at each in more detail. But before we do that, remember that CD4 cells vary from day to day. So do not be too discouraged if there is a little dip in your CD4 count or do not be too elated if there is a little rise in your CD4 count. Generally speaking, a significant difference between 2 tests is approximately a 30% change in absolute count.
Determining the urgency of starting ART
When to start ART has always been a controversial topic. There are many factors affecting this decision and you should always discuss this in detail with your doctor. In a nutshell, the CD4 count recommendations for initiating ART are:
< 350 cells/ mm3 – Strongly recommended to start ART. There is strong data from good clinical trials to support this.
350 – 500 cells/ mm3 – Also strongly recommended to start ART. There is also good data from clinical trials to support this although not as robust as for < 350 cells/mm3.
> 500 cell/ mm3 – Expert opinion is that patients will benefit from ART.
Update 3rd July 2013
The most recently published WHO’s Consolidated Guidelines on the use of Anti-Retroviral Drugs for treating and preventing HIV infection now recommends starting Anti-Retroviral therapy for ALL patients with CD4 cell counts of 500 or less.
Deciding if there is a need to prescribe medicines to prevent opportunistic infections
We are exposed to many organisms trying to infect us everyday. Normally our immune system can fight off these bugs without even bothering us. If a person’s immune system becomes very weak, like how a person is in late stages of HIV infection, the immune system becomes unable to fight off these organisms and they start to cause problems. This is what we term an opportunistic infection.
Deciding when and what medicines to give to prevent such opportunistic infections is complex. As a general rule, you would want to discuss the need for such treatment when the CD4 count drops below 200 cells/mm3 .
As a way to see if a person is responding to ART
If a person is responding well to ART, we expect to see a rise in the CD4 count of 50 to 150 cells/mm3 in the first year with most of the increase occurring in the first 3 months. Subsequent increases of 50 to 100 cells/mm3 per year is expected until a steady state is reached if the virus remains adequately suppressed by ART. Factors such as age and an initial low CD4 count may affect this.
What to expect
Your doctor would definitely want to measure your CD4 count during your first visit. That will be a key factor in deciding your treatment plan.
If your CD4 count is good, your doctor might want to defer ART. There are situations when doctors will recommend ART even when the CD4 count is healthy. This will be discussed in another article. If the decision is not to start ART, your doctor will tell you to re-visit regularly for CD4 count tests.
Without treatment, the CD4 count will inevitably fall over time (unless you are a long term non-progressor or an elite controller. This will be discussed in a separate article.) How fast and how low the CD4 count falls will help determine when you have to start ART.
Some patients are only diagnosed with HIV in the later stages. So during the first visit, the CD4 count might already be very low. In these situations, you doctor will not only start you on ART, he will also start you on various antibiotics to prevent opportunistic infections.
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About Dr. Tan
Dr. Tan graduated from the National University of Singapore in 2001. His residency was in the two largest public hospitals in Singapore; Tan Tock Seng Hospital and Singapore General Hospital.