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T-Cell Subset Analysis by Flow Cytometry (CD4/CD8 Ratio, Absolute Counts)

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

This test measures the number and balance of two key types of T-cells in your blood: CD4+ (helper) and CD8+ (cytotoxic) cells. It helps assess immune function, especially in conditions like HIV or autoimmune diseases.

Quick summary

["Helps evaluate immune health and response to treatments targeting T-cells."]

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

Key facts at a glance

LOINC
100431-6
Short code
T-cells LRBA MFI Bld FC
Synonyms
T-cells LRBA MFI Bld FC
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
flow-cytometry
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why This Test Matters for Your Health

T-cells are critical for fighting infections and managing immune responses. This test helps doctors track how well your immune system is functioning, especially if you have conditions like HIV, cancer, or autoimmune disorders. It may also be used to monitor treatment progress or side effects of medications that affect T-cells.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into your arm to draw a small amount of blood. The process takes about 5 minutes. If you’re on blood thinners, let your doctor know before the test.

How the Results Are Used

Your results will show the absolute counts of CD4+ and CD8+ T-cells, as well as their ratio. Lower CD4+ counts or imbalances may signal immune weakness, while higher CD8+ counts could indicate chronic infections or certain cancers. Your doctor will interpret these results in the context of your overall health and medical history.

Common Conditions This Test Helps Diagnose or Monitor

This test is often used in people with HIV/AIDS to track immune health, in cancer patients to monitor treatment effects, and in autoimmune diseases like rheumatoid arthritis or lupus. It may also be used to evaluate immune responses to vaccines or infections.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

T-cell count and ratio test

Frequently asked questions

What does a low CD4+ count mean?
A low CD4+ count (below typical reference ranges) may indicate a weakened immune system, often seen in HIV infection, advanced age, or certain medications that suppress immune function. It’s important to discuss your results with your healthcare provider to understand the full context.
How often should I get this test?
The frequency depends on your medical condition. For example, people with HIV may get this test every few months to monitor immune health. Others, like cancer patients, may have it more or less often based on their treatment plan. Always follow your doctor’s recommendations.
Can diet or supplements affect T-cell counts?
Diet and supplements can indirectly support immune health, but they do not directly affect T-cell counts measured by this test. Focus on a balanced diet rich in vitamins (like vitamin D, B12) and lean proteins to support overall immune function, but avoid excessive supplements without medical guidance.
  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