CD4 T-Cell Count (Absolute)
This test measures the number of CD4 cells (a type of white blood cell) in your blood. CD4 cells help fight infections and are important for immune function.
["CD4 cells are key to your immune system’s ability to defend against infections and diseases."]
Key facts at a glance
- LOINC
- 44056-0
- Short code
- CD4NAIVEBM
- Synonyms
- CD4+CD45RA+CD45RB+CD45RC+ Cells # Mar
- Category
- chemistry
- Sample
- serum
- Container
- EDTA (lavender-top) or heparin (green-top) sterile tube for bone marrow aspirate collected into anticoagulant medium. ACD (yellow-top) tube is acceptable as an alternative anticoagulant. Specimens must be maintained at room temperature (18-22°C) and processed within established stability windows. For serum, plain red-top or serum separator tube (SST) may be used per laboratory protocol.
- Units
- N/A
- Ref low
- 4.2
- Ref high
- 5.9
- Critical range
- 2 N/A – 7 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- Flow cytometry using multiparameter immunophenotyping with fluorochrome-conjugated monoclonal antibodies against CD4, CD45RA, CD45RB, and CD45RO (or CD45RC) surface markers, followed by absolute count determination using counting beads or volumetric analysis on a bone marrow aspirate specimen.
- CPT
- 86359 (T cells, total count); 86360 (T cells, absolute CD4 count); additional CPT codes may apply for comprehensive immunophenotyping panel including CD45RA, CD45RB, CD45RO/CD45RC subsets such as 88184, 88185 (flow cytometry interpretation), and 86356 (mononuclear cell antigen quantitation)
- SNOMED
- 443742003 |Bone marrow specimen|; 365632008 |Count of cells|; 116859006 |T-helper cell|; 25239000 |CD4-positive helper T lymphocyte|; 303852008 |Naive T lymphocyte|
- Specimen volume
- Minimum 1-2 mL of bone marrow aspirate collected into sterile anticoagulant-containing transport medium. First-pull aspirate is preferred for immunophenotyping to minimize hemodilution. For serum: minimum 1-2 mL whole blood yielding adequate serum for ancillary testing.
- Stability
- Bone marrow aspirate specimens must be processed within 24-48 hours of collection when maintained at room temperature (18-22°C). Do not refrigerate or freeze bone marrow specimens intended for flow cytometry, as cold exposure may cause cell clumping, loss of viability, and altered surface marker expression. Specimens older than 48 hours may yield unreliable results due to cell death and antigen degradation.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 24–72 hours
- Order
- routine
Why This Test Matters
CD4 cells are a critical part of your immune system. They help your body fight off infections like viruses, bacteria, and fungi. Low CD4 counts can indicate weakened immunity, which may increase your risk for serious infections or diseases, especially if you have HIV or another condition affecting your immune system.
What to Expect Before the Test
No special preparation is needed for this test. You’ll have a small needle inserted into your arm or hand to draw blood. The process usually takes a few minutes. If you’re on blood thinners or have a history of bleeding issues, let your provider know before the test.
What the Results Mean
Results are typically reported as a count of CD4 cells per microliter (cells/µL) of blood. While reference ranges vary slightly by lab, lower counts may suggest immune suppression, which could be linked to conditions like HIV or other immune disorders. Your doctor will interpret results in the context of your overall health and medical history.
Common Causes of Low CD4 Counts
Low CD4 counts can result from infections (like HIV), certain medications (e.g., some chemotherapy drugs), autoimmune diseases, malnutrition, or chronic illnesses. If you notice unexplained infections, fatigue, or weight loss, discuss your results with your healthcare provider.
Reference range
Adult males: 4.2-5.9; Females: 3.8-5.1 x 10^12/LN/A
No special patient preparation required for serum specimen collection. For bone marrow aspirate evaluation, patient consent for the procedure must be obtained. Recent corticosteroid therapy, chemotherapy, radiation, immunosuppressive agents, or bone marrow-stimulating factors (e.g., G-CSF) may affect results and should be documented. Discontinue heparin therapy prior to bone marrow aspiration when possible to minimize clotting of aspirate.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: Monitoring Immune Health
Short name
CD4 Count
Frequently asked questions
What does a low CD4 count mean for my health?
How often should I get this test?
Can I do anything to support my CD4 cell count?
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 17, 2026. · Read our editorial policy