CD4 count (T cell count) - for patients with known HIV serology
The CD4 count is used to monitor disease progression in HIV
infection. For example, patients with counts below 200 x 106/L are
at risk of pneumocystis pneumonia and should received antibiotic
prophylaxis. CD4 counts are also used to inform decision making on
anti-retroviral therapy. BHIVA publish guidelines on CD4 counts and
Apart from HIV infection, the CD4 count can be reduced by acute
and chronic stress, including infections and physical or
psychological stress. CD4 counts are also affected by daily
circadian rhythms and the menstrual cycle.
Specimen transport: An EDTA specimen should
arrive in the lab on the same day or within 48 hours maximum.
Samples should be stored and transported at room temperature and
Repeat frequency: Three times a year in
asymptomatic patients, more frequently in those with symptoms
when medication is being changed.
Special precautions: None
Normal reference range: (95% confidence
||1 wk - 2 mo
Paediatric reference ranges are from Comans-Bitter WM, et al,
"Immunophenotyping of Blood Lymphocytes in Childhood," J
Paediatrics, 1997, 130:388-393
Volume and sample type: 5ml EDTA blood
Method: Flow cytometry - single platform
Turnaround time (calendar days from sample
receipt to authorised result): Median - 1, 95th percentile - 3
Indications for the test: For use as a
monitoring tool in serologically confirmed HIV infection. Should
not be used in an attempt to diagnose HIV infection.
Factors affecting the test: Because
physiological stress can affect results, avoid testing during acute
infections, postoperatively etc. Always try and do monitoring tests
at the same time of day. In women, try to do monitoring tests at
the same phase of the menstrual cycle.
Clinical workstation reference: CD4 COUNT
(Last updated December 1st