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CD19+ B Cell Count in Peripheral Blood (Absolute)

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

This test measures the number of CD19+ cells, a type of white blood cell involved in immune function, found in your blood. It helps assess immune health, particularly in conditions affecting B cells.

Quick summary

["This test helps evaluate your immune system’s B cell activity and may guide treatment decisions for certain blood disorders."]

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

Key facts at a glance

LOINC
17829-3
Short code
CD19BF
Synonyms
CD19 Cells NFr Fld
Category
chemistry
Sample
serum
Container
Sterile, leak-proof container for body fluid collection; EDTA (lavender-top) tube preferred for peripheral blood anticoagulation if simultaneous blood analysis is needed. Transport at room temperature or 4°C.
Units
N/A
Ref low
5
Ref high
15
Fasting
false
Population
adult
Sex
all
Age range
≥ 0 years
Method
Flow cytometry using fluorescently labeled monoclonal antibodies against CD19 surface marker; cells identified and enumerated by multiparameter immunophenotyping
CPT
86356
SNOMED
1421000119106
Specimen volume
Minimum 1-2 mL of body fluid; larger volumes (5-10 mL) preferred for cell yield optimization, especially from low-cellularity fluids such as cerebrospinal fluid
Stability
Process within 1-4 hours of collection for optimal viability. If delayed, refrigerate at 2-8°C; samples should be analyzed within 24 hours. Viability decreases significantly after 24-48 hours.
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Is Done

Doctors may order this test if you have symptoms like frequent infections, autoimmune diseases, or if you’re undergoing treatment for conditions like leukemia, lymphoma, or immune deficiencies. It can also be part of monitoring for immune-related side effects from medications.

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 is quick and typically painless. If you’re nervous, let your healthcare provider know.

What the Test Results Mean

Results show the absolute count of CD19+ B cells per microliter of blood. Lower than expected counts may indicate immune deficiencies or certain cancers, while higher counts could be seen in overactive immune responses or some infections.

Common Conditions Affecting Results

Abnormal counts can occur in conditions like chronic infections, autoimmune diseases (e.g., lupus), or after treatments like chemotherapy or radiation. Always discuss results with your doctor.

Reference range

Reference values vary by specimen type and laboratory. In peripheral blood, CD19+ B-lymphocytes typically comprise 5-15% of total lymphocytes or 100-500 cells/μL. Body fluid reference ranges must be established by the performing laboratory.N/A

Specimen: serum

No special patient preparation required. If patient is on immunosuppressive or immunomodulatory therapy, document recent medication administration as results may be affected.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

This test is critical in diagnosing and managing immune-related disorders, particularly those affecting B cells. It helps track disease progression, response to treatment, or immune system recovery post-treatment. For example, it may be used in monitoring B-cell lymphoma or autoimmune diseases like systemic lupus erythematosus.

Short name

CD19+ B Cell Count

Frequently asked questions

What does a low CD19+ B cell count mean?
A low count may suggest an immune deficiency, such as selective IgA deficiency or other B-cell-related disorders. It could also indicate treatment effects (e.g., chemotherapy) or certain infections. Your doctor will interpret results in the context of your symptoms and medical history.
Can this test detect early signs of B-cell cancers like lymphoma?
Yes, this test can help identify abnormal B-cell populations, which may be present in early-stage B-cell cancers or other hematologic malignancies. However, it’s often used alongside other tests (like imaging or biopsies) for a full diagnosis.
Does fasting affect this test?
No, fasting is not required for this blood test. It measures cells, not substances like blood sugar or lipids, so diet won’t influence 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