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Blood Test Results

Reading the signals - understanding CD4 and viral load tests

Blood tests are important for monitoring how well your immune system is functioning, how effectively any treatment is working, and HIV disease progression.

CD4 (T-Cell) Test

CD4 cells are a type of white blood cell. The immune system is made up of many different types of white blood cells. CD4 cells play an important protective role in an immunity – the more you have, the stronger your defences to HIV and other infection. A good CD4 count is between 350 and 1200. This number can change dramatically between blood tests, so it's important to maintain an overall picture over time.

A CD4 count is a measure of how well your immune system is functioning, especially in relation to HIV. A CD4 count provides a good indicator for deciding when to treat and how well treatment is working.

In order to reproduce, or copy itself, the HIV virus must enter a CD4 cell and implant itself in the genetic material (DNA). CD4 cells recognise HIV when it enters and in response send out chemical messages to help coordinate the immune system’s defences to HIV. This process eventually results in the death of the CD4. Even though you are constantly making new CD4's, HIV will eventually prevent the body from producing enough CD4's to maintain continuous immune protection. This is where we get the term immuno-suppressed, meaning weakened immune system.

Viral Load

Viral load is the amount of virus in your bloodstream. The result is given as the number of 'copies’ of HIV per millilitre of blood, (copies/ml). When a result is referred to as ‘undetectable’, it doesn’t mean the virus has been cleared or cured. It means the amount of HIV present in the blood is so small it can’t be measured. In Australia this usually means less than 50 copies/ml. The lower your viral load, the slower HIV is reproducing.

Knowing the amount of HIV in the bloodstream helps predict future damage to your immune system. By monitoring viral load, along with CD4 counts, timely choices can be made about when to start treatment. Viral load tests are also important indicators of how effectively treatment is working.

CD4 Percentage

This measures the proportion of CD4 in every 100 lymphocytes (white blood cells that include T-cells and B-Cells). Together with viral load and actual CD4 cell tests, it’s helpful for deciding when to treat. A CD4 percentage below 17%, with a viral load above 100,000 and CD4 count of 200-350 or lower, indicates serious risk of HIV disease progression.

More tests your doctor might administer

Cholesterol and Triglyceride Levels
The two major fats (lipids) in the blood are triglycerides and cholesterol. Glucose, triglyceride, and cholesterol levels are most reliably measured in the morning before breakfast. Certain combinations of anti-HIV therapies are thought to increase cholesterol, triglyceride and glucose levels in some persons which may increase the risk of heart attack and stroke, and which can be a sign of lipodystrophy.

Liver Function Tests
There are a range of tests which taken together give an indication of the health of the liver. The liver can be damaged by hepatitis, alcohol and other drugs, and by HIV antiviral drugs. So it's important to keep a watch on liver function.

Kidney Function
Kidney function is normally measured by the levels of 'waste' products such as uric acid and creatinine. Some HIV antiviral drugs can affect the levels of these waste products because they compete with them for excretion in the kidney. Some HIV antiviral drugs may have an impact on kidney function.

Platelet Count
Platelets are important in helping your blood clot in response to a cut or wound. Some HIV antiviral drugs – particularly nucleoside analogues (eg. AZT, d4T) – can decrease the platelet count.

Haemoglobin and Haematocrit
Haemoglobin measures the levels of the key protein which transports oxygen around the body. Haematocrit is a measure of the proportion of blood that is red blood cells. Low haemoglobin levels or a low haemotocrit can be an indicator of anaemia – a known side effect of some HIV antiviral drugs.

HIV treatments are advancing rapidly. Explore this site for more about testing and stay in the loop on other issues.