CD4 Cell Count (Absolute)
This test measures the number of CD4 cells (a type of white blood cell) in your blood. CD4 cells help your immune system fight infections.
["CD4 cells are key to immune health; low levels may indicate immune weakness."]
Key facts at a glance
- LOINC
- 17825-1
- Short code
- CD41A
- Synonyms
- CD41a Cells NFr Bld
- Category
- chemistry
- Sample
- whole-blood
- Container
- EDTA (purple-top) vacuum blood collection tube for immunophenotyping; sodium citrate (blue-top) tube may be used for platelet function studies.
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 0 years
- Method
- Flow cytometry using fluorescently labeled monoclonal antibodies against CD41a (platelet glycoprotein IIb/IIIa complex), with analysis performed on whole blood specimens.
- CPT
- 86356
- SNOMED
- 395146001
- Specimen volume
- 3-5 mL of whole blood for adults; minimum 1 mL for pediatric patients. Submit whole blood tube at room temperature. Do not centrifuge.
- Stability
- Specimen should be analyzed within 24 hours of collection when stored at room temperature (20-25°C). Refrigeration may cause platelet activation and clumping. Specimens older than 24 hours may show decreased CD41a expression due to platelet degradation.
- Hemolysis max
- 100
- Lipemia max
- 200
- Icterus max
- 20
- TAT
- 24–72 hours
- Order
- routine
Why This Test Is Done
Your doctor may order a CD4 cell count to check your immune system, especially if you have HIV, another immune disorder, or are planning certain treatments that could affect your immune response. It can also help monitor how well your immune system is responding to treatment.
How the Test Works
A small sample of blood is taken from your arm and sent to a lab. The lab analyzes the blood to count your CD4 cells. This test does not involve any special preparation.
What to Expect Before or After the Test
You may feel slight discomfort from the needle used to draw blood, but it usually goes away quickly. There’s no downtime afterward. If you’re on blood-thinning medication or have a bleeding disorder, let your doctor know before the test.
Possible Results and Their Meaning
CD4 cell counts vary by age and health, but lower counts generally mean your immune system may not be working as well as it should. Your doctor will interpret the results in the context of your overall health and medical history.
Reference range
Results expressed as percentage of cells positive for CD41a and absolute count. Reference ranges vary by laboratory; typically CD41a+ cells represent the platelet/ megakaryocyte lineage. Normal platelet expression of CD41a: >90% of platelets positive. Abnormal expression patterns may indicate platelet glycoprotein deficiencies such as Glanzmann thrombasthenia.N/A
No fasting required. Patient should avoid aspirin, NSAIDs, and other platelet-inhibiting medications for at least 7-10 days prior to testing if possible, as these may interfere with platelet function analysis. Confirm medication restrictions with ordering physician.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
CD4 T-Cell Count
Frequently asked questions
How often do I need this test?
What if my CD4 count is low?
Does diet or exercise affect CD4 cell counts?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 11, 2026. · Read our editorial policy