Skip to content

B-cell count (CD19+ cells in whole blood)

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

This test measures the number of B cells (a type of white blood cell) marked by the CD19 protein, which is found on nearly all mature B cells. It helps assess immune function and detect conditions affecting B cells.

Quick summary

["This test helps evaluate your immune system and identify B-cell-related disorders."]

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

Key facts at a glance

LOINC
59143-8
Short code
CD19CD38
Synonyms
CD19+CD38+ Cells NFr Bld
Category
chemistry
Sample
whole-blood
Container
EDTA anticoagulant tube (lavender/purple-top, K2-EDTA or K3-EDTA). Sodium heparin (green-top) is also acceptable for flow cytometry. ACD-A (yellow-top) tubes may be used for extended stability requirements.
Units
N/A
Ref low
5
Ref high
20
Fasting
false
Population
adult
Sex
all
Age range
0–120 years
Method
Flow cytometry (immunophenotyping) using fluorescently labeled monoclonal antibodies against CD19 and CD38 surface markers, typically with CD45 gating and viability staining
CPT
88184 (Flow cytometry, cell surface, cytoplasmic, or nuclear marker, technical component only); 88185 (each additional marker, per antibody); 88187-88189 (interpretation services may apply)
SNOMED
1421000119104 | Measurement of CD19 and CD38 positive cells in blood by flow cytometry (procedure)
Specimen volume
Minimum 3-5 mL of whole blood for adults; 1-2 mL for pediatric patients. Smaller volumes may be acceptable with specialized microtube protocols for flow cytometry.
Stability
Specimen should be processed within 24-48 hours of collection when stored at room temperature (18-25°C). Refrigeration (2-8°C) may extend stability to 48-72 hours, but viability and marker expression may decline. Do not freeze whole blood specimens. Optimal results are obtained when analysis is performed within 24 hours of collection.
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–72 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may order this test if you have symptoms or conditions linked to B-cell dysfunction, such as recurrent infections, autoimmune diseases, or certain cancers (e.g., lymphoma). It may also be used during monitoring for immune-related treatments.

What to Expect Before the Test

No special preparation is needed. You’ll provide a small sample of whole blood drawn from your arm, similar to a routine blood draw. The sample is processed to count CD19+ cells.

What the Results Mean

Results are typically reported as an absolute cell count (number of CD19+ cells per microliter of blood). Lower than expected counts may indicate immune deficiencies or B-cell disorders, while higher counts could suggest overactive B-cell activity.

Common Conditions Monitored

This test is often used to monitor B-cell-related conditions like chronic lymphocytic leukemia (CLL), autoimmune diseases (e.g., lupus), or immune deficiencies. It can also guide treatment decisions for conditions affecting B cells.

Reference range

Reference ranges vary by laboratory and patient population. CD19+CD38+ B-cell subsets are typically reported as a percentage of total lymphocytes or absolute count (cells/μL). Adult reference values for CD19+CD38+ cells generally range from 5-20% of total B lymphocytes, with absolute counts varying by age. Pediatric values differ significantly and should be interpreted using age-matched reference ranges.N/A

Specimen: whole-blood

No special patient preparation required. Patients on immunosuppressive therapy (e.g., rituximab, corticosteroids) may show altered results and should be reported to the laboratory. Recent vaccination, infection, or stress may transiently affect lymphocyte subset distribution. Inform the laboratory of any recent blood transfusions, as they may affect results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

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, chronic immune activation, or certain cancers (e.g., B-cell lymphoma). Your provider will discuss findings in the context of your symptoms and medical history.
Does this test require fasting?
No fasting is required for this test. Blood is drawn at a time convenient for you, and results focus on cell counts rather than biochemical measurements.
How often should I get this test?
Frequency depends on your condition. If you have a chronic B-cell disorder, your provider may recommend periodic testing (e.g., every few months). Follow their guidance for ongoing monitoring.
  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