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CD19+ B-Cell Lymphocyte Count (Absolute)

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

This test measures the number of CD19+ cells in your blood, which are a type of white blood cell involved in immune function. CD19 is a protein found on the surface of B-cells, a key part of the immune system.

Quick summary

["CD19+ cells help fight infections and contribute to immune responses; this test helps assess immune health or monitor conditions affecting B-cells."]

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

Key facts at a glance

LOINC
20593-0
Short code
CD19
Synonyms
CD19 Cells NFr Spec
Category
chemistry
Sample
serum
Container
EDTA (lavender-top) or heparinized (green-top) tube for whole blood; sterile container for tissue/bone marrow specimens
Units
N/A
Ref low
5
Ref high
15
Fasting
false
Population
adult
Sex
all
Age range
0–120 years
Method
Flow cytometry using fluorescently-labeled monoclonal antibodies against CD19 surface marker, typically performed on whole blood or bone marrow specimens
CPT
86355
SNOMED
116981002
Specimen volume
3-5 mL of whole blood; minimum 1 mL for pediatric or tissue specimens
Stability
Specimen should be processed within 24-48 hours of collection. Store at room temperature (18-22°C). Do not refrigerate. Specimen stability may vary by laboratory protocol.
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
24–72 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may order this test to evaluate immune function, diagnose or monitor conditions like chronic lymphocytic leukemia (CLL), lymphoma, or other B-cell-related disorders. It may also be used before or after treatments that affect the immune system, such as chemotherapy or bone marrow transplants.

What to Expect Before the Test

No special preparation is needed. You may have a simple blood draw, usually done in a clinic or lab. The process is quick and typically painless. If you’re on blood-thinning medication, let your provider know before the test.

What the Test Results Mean

Results show the absolute count of CD19+ cells per microliter of blood. Abnormal counts (either high or low) may indicate immune system issues or diseases affecting B-cells. Your provider will interpret results in the context of your overall health and medical history.

Common Conditions Monitored or Diagnosed

This test is often used to diagnose or monitor conditions such as B-cell lymphoma, chronic lymphocytic leukemia, or other immune-related disorders. It can also help track the effectiveness of treatments targeting B-cells.

Reference range

Reference ranges vary by laboratory and specimen type. CD19+ B-lymphocytes typically represent 5-15% of total lymphocytes in peripheral blood. Absolute counts vary by age.N/A

Specimen: serum

No special patient preparation required. Recent immunotherapy (e.g., rituximab, CAR-T therapy), chemotherapy, or immunosuppressive medications may significantly affect CD19+ cell counts. Inform the laboratory of relevant clinical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: CD19+ Cells Play a Critical Role in Immune Defense

Short name

CD19+ Cells

Frequently asked questions

How is the test performed?
The test involves drawing a small amount of blood, which is then analyzed in a lab to count the CD19+ cells. The sample is typically processed using flow cytometry, a technique that identifies and counts specific cell types based on their surface proteins.
What if my test results are abnormal?
If your results show an abnormal count of CD19+ cells, your healthcare provider will discuss potential causes, which could include immune disorders, infections, or certain medications. They may recommend further testing or adjustments to your treatment plan.
Can I eat or drink before this test?
No special diet or fasting is required for this test. However, if you’re scheduled for a blood draw, avoid eating or drinking for at least 8–12 hours before the procedure to ensure accurate 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