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Absolute Counts of CD3+ and CD4+ T Cells (Peripheral Blood)

Published: August 9, 2026Updated: August 16, 2026

This test measures the number of two key types of T cells—those that help regulate immune responses—in your blood. These cells play a critical role in fighting infections and maintaining immune health.

Quick summary

["Your doctor may order this test to check immune function or monitor conditions affecting T cells."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
97599-5
Short code
CD4CD8LR
Synonyms
CD3+CD4+ Cells/CD3+CD8+ Cells L resp FC
Category
chemistry
Sample
serum
Container
Sterile, leak-proof specimen container for bronchoalveolar lavage (BAL) fluid or lower respiratory aspirate; transfer to flow cytometry-compatible tubes containing anticoagulant (EDTA or heparin) for cell preservation.
Units
N/A
Ref low
1
Ref high
4
Critical range
0.5 N/A – —
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
flow-cytometry
CPT
86359 (T cells, total count); 86360 (T-helper/CD4); 86361 (T-suppressor/CD8); additional flow cytometry codes may apply
SNOMED
36464000 (Bronchoalveolar lavage fluid specimen); 40710006 (Helper T cells); 41788000 (Suppressor T cells)
Specimen volume
Minimum 2-5 mL of lower respiratory specimen (BAL fluid, bronchial washings, or brushings); larger volumes (10-50 mL for BAL) preferred when feasible
Stability
Specimen should be processed within 2-4 hours of collection to maintain cell viability. Refrigerate at 2-8°C if processing is delayed; do not freeze. Viability decreases significantly beyond 24 hours.
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Is Done

Doctors may request this test to evaluate immune system health, diagnose immune disorders, or assess how well your body is responding to treatments for conditions like HIV, autoimmune diseases, or cancer. It can also help monitor immune recovery after illness or treatment.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into a vein (usually in your arm) to draw blood. The process takes about 5 minutes, and you may feel a brief pinch. You can eat and drink normally before the test.

What the Results Mean

Results show the absolute counts of CD3+ (total T cells) and CD4+ (helper T cells) cells per microliter of blood. Lower counts may indicate immune suppression, infection, or certain diseases. Your doctor will interpret these numbers in the context of your overall health and medical history.

Common Conditions Monitored

This test is often used to monitor HIV infection, where CD4+ counts are closely tracked to assess immune status. It may also help diagnose or manage conditions like leukemia, lymphoma, or autoimmune diseases where T cell function is affected.

Reference range

CD4/CD8 ratio in lower respiratory specimens is interpreted in clinical context; generally a ratio >1.0 suggests preserved immune competence, while values <1.0 may indicate immune dysregulation. Absolute lymphocyte subset counts are specimen-dependent.N/A

Specimen: serum

No fasting required. Patient should be informed about the bronchoscopy or sputum induction procedure. Prior to lower respiratory specimen collection, inform the provider of any current anticoagulant therapy. Recent immunosuppressive therapy or biologic agents should be disclosed.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

T Cell Subset Counts

Frequently asked questions

What Does a Low or High Count Indicate?
A low CD4+ count (below normal) is often linked to weakened immunity, higher risk of infections, or diseases like HIV progression. A low CD3+ count may suggest immune dysfunction, but it’s less specific. High counts alone usually aren’t concerning unless paired with other symptoms or conditions.
How Often Should I Get This Test?
Frequency depends on your health needs. For example, people with HIV may get repeated tests to track immune health. Your doctor will determine how often you need this test based on your diagnosis and treatment plan.
Can I Fast Before This Test?
No fasting is required for this blood test. However, always inform your doctor about any medications or supplements you’re taking, as they may affect results.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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