Skip to content

Absolute Count of CD19+ B Cells in Whole Blood

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

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

Quick summary

["This test helps assess your immune system’s B cell activity."]

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

Key facts at a glance

LOINC
8116-6
Short code
CD19
Synonyms
CD19 Cells # Bld
Category
chemistry
Sample
whole-blood
Container
EDTA (lavender/purple-top) vacutainer tube; alternatively, sodium heparin (green-top) tube may be used for flow cytometry immunophenotyping.
Units
N/A
Ref low
100
Ref high
500
Critical range
50 N/A – —
Fasting
false
Population
adult
Sex
all
Age range
≥ 0 years
Method
Flow cytometry using fluorescently labeled monoclonal antibodies against CD19 surface marker, typically with CD45 gating and viability dyes; results reported as absolute count per unit volume of whole blood.
CPT
86355
SNOMED
395124008
Specimen volume
3–5 mL of whole blood for adults; minimum 1 mL for pediatric patients.
Stability
Specimen should be processed within 24–48 hours of collection when stored at room temperature (18–25°C). Do not refrigerate or freeze, as this can cause cell loss and altered surface marker expression. If delayed, use cell-stabilizing tubes per laboratory protocol.
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may order this test if you have symptoms or conditions that suggest an abnormal B cell count, such as recurrent infections, autoimmune diseases, or certain types of cancer. It could also be part of monitoring for immune-related treatments.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into a vein in your arm to draw a blood sample. The process usually takes a few minutes.

What the Test Results Mean

Results are typically reported as the absolute count of CD19+ B cells per microliter of blood. While reference ranges vary by lab, lower than expected counts may indicate immune deficiencies, while higher counts could suggest overactive immune responses or certain blood disorders.

Common Conditions Monitored or Diagnosed

This test is often used to diagnose or monitor conditions like chronic lymphocytic leukemia (CLL), other lymphoproliferative disorders, or immune deficiencies such as common variable immunodeficiency (CVID).

Reference range

Absolute CD19+ B-lymphocyte count in healthy adults: 100–500 cells/μL (0.1–0.5 × 10⁹/L); pediatric reference ranges are higher and age-dependent, with neonates and infants showing higher B-cell counts.N/A

Specimen: whole-blood

No fasting required. Patient should be well-hydrated. Avoid recent immunizations (live vaccines) for at least 4 weeks prior when possible, as they may transiently alter lymphocyte subsets. Inform the laboratory of any recent immunosuppressive therapy, corticosteroids, or biologic agents.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CD19+ B Cell Count

Frequently asked questions

How long does it take to get the results of this test?
Test results are typically available within 1 to 3 business days, depending on your lab’s processing schedule. Your healthcare provider will discuss the results with you during your follow-up visit.
Can I eat or drink before this blood test?
You can eat and drink normally before this test. No fasting is required.
Is there any pain or discomfort associated with this test?
Most people experience only mild discomfort or a slight pinch when the needle is inserted. The area may feel sore for a few minutes afterward, but this usually goes away quickly.
  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