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CD19 and CD20 B-Cell Lymphocyte Counts (Qualitative/Quantitative Immunophenotyping)

Published: August 9, 2026Updated: August 15, 2026

This test evaluates the presence and proportion of CD19 and CD20 markers on B-cells in your blood, often used to assess immune cell populations or diagnose conditions like lymphoma or leukemia.

Quick summary

["Helps diagnose blood cancers or immune disorders by checking specific B-cell markers."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 15, 2026Editorial policy

Key facts at a glance

LOINC
94689-7
Short code
CD20CD19
Synonyms
CD20 Cells/Cells.CD19 NFr Bld
Category
chemistry
Sample
whole-blood
Container
EDTA (lavender/purple-top) blood collection tube; sodium heparin (green-top) acceptable alternative
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
0–120 years
Method
Flow cytometry using fluorochrome-conjugated monoclonal antibodies against CD20 and CD19 surface markers, with ratio calculation
CPT
86355
SNOMED
444100007
Specimen volume
3-5 mL whole blood (minimum 1 mL for pediatric patients); 5 mL preferred for adult flow cytometry panels
Stability
Room temperature: 24-48 hours (process within 24 hours preferred); Refrigerated (2-8°C): up to 48 hours. Do not freeze. Viability and marker expression may decline with prolonged storage.
Hemolysis max
100
Lipemia max
100
Icterus max
50
TAT
4–24 hours
Order
routine

Why This Test Is Done

Doctors may order this test to diagnose or monitor conditions such as chronic lymphocytic leukemia (CLL), non-Hodgkin lymphoma, or other B-cell-related cancers. It can also help track treatment responses or rule out immune system abnormalities.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into your arm or vein to draw a blood sample. The process takes a few minutes, and you may feel a brief pinch. If you’re nervous, let your healthcare provider know.

What the Results Mean

Results show the percentage or absolute count of CD19+ and CD20+ cells in your blood. Abnormal findings may indicate an overproduction of B-cells (e.g., cancer) or other immune-related issues. Your doctor will interpret these results in the context of your symptoms and medical history.

Common Conditions This Test Helps Diagnose

This test is critical for diagnosing blood cancers like chronic lymphocytic leukemia (CLL), follicular lymphoma, and other B-cell lymphomas. It may also help identify immune disorders or monitor treatment progress in patients undergoing chemotherapy or immunotherapy.

Reference range

CD20/CD19 ratio: typically >0.95 (≥95%) in healthy individuals, as nearly all CD19+ B lymphocytes co-express CD20. Absolute CD19+ B cell counts vary by age with higher levels in children that decline to adult ranges by adolescence.N/A

Specimen: whole-blood

No special preparation required. Patients should inform the laboratory of any recent immunomodulatory therapy including rituximab, obinutuzumab, or other anti-CD20 monoclonal antibody treatments. Recent corticosteroid use or chemotherapy may affect results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: How Results Guide Treatment

Short name

B-Cell Immunophenotyping (Screen/Confirm)

Frequently asked questions

How will my test results affect my treatment plan?
Your doctor will use these results to determine if you have a B-cell-related condition, guide treatment decisions (e.g., chemotherapy, targeted therapies), or assess whether your immune system is functioning normally. For example, elevated B-cell counts might suggest leukemia, while abnormal proportions could indicate an immune disorder.
What if my test results are abnormal?
If your results show unusual CD19/CD20 cell counts, your doctor may recommend further testing, such as a bone marrow biopsy, or additional bloodwork to confirm a diagnosis. Follow-up care will depend on your specific condition and treatment needs.
Can I prepare for this test differently if I’m on certain medications?
Generally, no special dietary or medication adjustments are needed. However, if you’re on blood-thinning medications (e.g., warfarin) or have a history of bleeding disorders, inform your doctor beforehand to ensure safe blood drawing.
  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 15, 2026. · Read our editorial policy