B-cell count (per microliter of whole blood)
This test measures the number of B cells, a type of white blood cell involved in immune response, found in your blood.
["B-cell counts help assess immune function and detect conditions affecting B cells."]
Key facts at a glance
- LOINC
- 20592-2
- Short code
- CD19
- Synonyms
- CD19 Cells # Spec
- Category
- chemistry
- Sample
- serum
- Container
- Lavender-top (EDTA) anticoagulant tube for whole blood flow cytometry; alternatively heparinized tube
- Units
- N/A
- Ref low
- 90
- Ref high
- 660
- Critical range
- 20 N/A – —
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- Flow cytometry using fluorescently labeled monoclonal antibodies against CD19 surface marker; results reported as absolute count calculated from white blood cell differential and lymphocyte percentage
- CPT
- 86356
- SNOMED
- 116646005
- Specimen volume
- 3-5 mL whole blood; minimum 1 mL for pediatric patients
- Stability
- Room temperature: 24 hours; refrigerated (2-8°C): 48 hours; do not freeze. Specimen should be processed within 24 hours for optimal CD19 antigen preservation.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why Is This Test Done?
Your healthcare provider may order this test to evaluate immune health, diagnose or monitor conditions like chronic lymphocytic leukemia, immune deficiencies, or autoimmune diseases. It may also be used during cancer treatment to check for B-cell-related side effects or responses to therapy.
What Does a Low or High Count Mean?
Low B-cell counts may suggest immune disorders, infections, or certain cancers. High counts could indicate overactive immune responses or conditions like multiple myeloma. However, results alone don’t diagnose a specific condition—your provider will consider your full medical picture.
Sample Collection and Preparation
A blood sample is drawn from a vein, usually in your arm. The blood is processed to count B cells using advanced laboratory techniques, often involving flow cytometry to identify and quantify these cells.
Common Conditions Monitored
This test is frequently used in the context of blood cancers (e.g., lymphoma), immune disorders (e.g., systemic lupus erythematosus), or to monitor immune recovery after treatments like chemotherapy or radiation.
Reference range
Adults: 90-660 cells/μL (0.09-0.66 x 10^9/L); approximately 5-20% of total lymphocytesN/A
No special preparation required. Inform laboratory of current medications, especially recent rituximab or other B-cell depleting therapy. Avoid exercise immediately prior to collection as it may transiently alter lymphocyte counts.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
B-Cell Count
Frequently asked questions
What Might Cause Abnormal Results?
How Often Is This Test Done?
Can I Prepare for This Test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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