CD4 Count

A CD4 test is performed after the detection of HIV in blood. As a decreasing number of CD4+ cells is a sign of disease progression, it is an important test to classify the patient into different stages of immunodeficiency.

A CD4 test is also required as an objective tool to help decide the initiation and choice of antiretroviral therapy (ART). The responsiveness to ART is also assessed based on the changes in CD4+ cell count.

Along with CD4 test,  plasma viral load test is also a sensitive indicator of the progression of  HIV infection. However, since it is a more expensive test to perform, CD4 test remains the test of choice to measure disease progression.

A CD4 test may also be performed after organ transplants to detect whether the body has accepted the donor organ successfully or not.

CD4 test does not require any special preparations.

A small quantity of blood is withdrawn from a vein in the arm by inserting a needle. The sample is collected into a syringe and stored in a container. Only a small quantity of blood is required for this test. The individual will feel a momentary pain on needle insertion but the test itself is risk-free. Sampling process does not usually take more than five minutes.

Normal results: The normal range of CD4+ cells is 410-1590 cells per cubic millimetre (/mm3). If test results are within this range, it indicates that the ART is effective. However, results must only be interpreted in terms of the clinical question at hand. This test must not be used as a substitute for HIV test, as many acute viral and bacterial infections, as well as other medical problems, can also lead to a reduction in CD4+ cell count.

Abnormal results: A cell count range between 250 and 500 cells/mm3 signifies a weakened immune system, and the individual may be prone to serious bacterial infections, such as pneumonia; meningitis; pulmonary tuberculosis (TB); and fungal infections, such as oral candidiasis. He/she may have other unexplained symptoms, such as persistent diarrhoea, for more than one month, with drastic weight loss of greater than 10% of body weight, persistent fever and anaemia.

If the CD4 test shows a range below 200 cells per cubic millimetre, it is indicative that the HIV has led to full-blown acquired immunodeficiency syndrome (AIDS). The symptoms of AIDS include:

• HIV wasting syndrome
• Recurrent severe bacterial pneumonia
• Chronic herpes simplex infection around the genitalia, which persists for more than one month
• Oesophageal candidiasis or candidiasis of the trachea, bronchi or lungs
• Extra-pulmonary TB, ie tuberculosis not restricted to the lungs and affecting other organs such as the spine
• Kaposi sarcoma, a disease in which malignant skin tumours originate from blood vessels
• Toxoplasmosis of the central nervous system
• HIV encephalopathy
• Symptomatic HIV-associated nephropathy or HIV-associated cardiomyopathy

Low values of CD4+ cells must also be clinically correlated to begin ART. Initiation of ART is recommended when CD4+ levels are below 350 cells/mm3, and the individual is suffering from pulmonary TB or any other serious bacterial infection.

Benefits of ART outweigh the risk to a pregnant woman and the foetus when the CD4+ count is less than 350 cells/mm3, and the woman has contracted any of the severe conditions mentioned above.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational perspective and is in no way a substitute for medical advice from a qualified doctor.