CD4 Cell Count (Absolute)
This test measures the number of a specific type of white blood cell called CD4 cells, which play a key role in the immune system. CD4 cells help fight infections and are often monitored in conditions affecting immunity.
["CD4 cells help protect your body against infections and diseases; low levels may signal immune weakness."]
Key facts at a glance
- LOINC
- 17149-6
- Short code
- CD42A
- Synonyms
- CD42a Cells NFr Bld
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lavender-top (EDTA) or sodium citrate tube; CTAD tube preferred for platelet function studies
- Units
- N/A
- Ref low
- 95
- Ref high
- 100
- Critical range
- 50 N/A – —
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- Flow cytometry using fluorescently labeled monoclonal antibodies specific for CD42a (GPIX) platelet glycoprotein
- CPT
- 88184
- SNOMED
- 395124008
- Specimen volume
- 3-5 mL of whole blood collected in appropriate anticoagulant tube
- Stability
- Specimen should be processed within 4-6 hours of collection. Samples may be held at room temperature (18-25°C) but should not be refrigerated, as cold activates platelets.
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
Why This Test Is Done
Your doctor may order a CD4 cell count to evaluate your immune system, especially if you have HIV/AIDS, certain cancers, or other conditions that weaken immunity. It can also help monitor treatment progress or assess risk for infections.
What to Expect Before the Test
No special preparation is needed. You’ll provide a blood sample, usually drawn from a vein in your arm. The process is quick and typically painless. If you’re on blood thinners, let your doctor know before the test.
What the Results Mean
Results are reported as a count of CD4 cells per microliter (cells/µL) of blood. While reference ranges vary by lab, lower counts may indicate immune suppression, while higher counts may suggest normal or overactive immune function. Your doctor will interpret results in the context of your overall health.
Common Conditions Monitored
CD4 cell counts are critical in diagnosing and managing HIV/AIDS, where low counts correlate with disease progression. They’re also used in cancer treatments (e.g., chemotherapy) to track immune recovery or side effects.
Reference range
CD42a expression is typically reported as percentage of platelets positive for CD42a or as mean fluorescence intensity (MFI). Reference ranges vary by laboratory; generally >95% of platelets express CD42a in healthy individuals.N/A
No fasting required. Patients should avoid aspirin and other antiplatelet medications for at least 7-10 days prior to testing when possible, as these may affect platelet function analysis. Inform the laboratory of any recent platelet transfusions.
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 will I need this test?
What happens if my CD4 count is low?
Can I eat or drink before the test?
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 16, 2026. · Read our editorial policy