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B-cell CD19 Immunoglobulin G (IgG) Quantification in Peripheral Blood Cells

Published: August 9, 2026Updated: August 15, 2026

This test measures the amount of Immunoglobulin G (IgG) produced by B cells in your blood. IgG is a key part of your immune system and helps fight infections.

Quick summary

["Understanding your B-cell IgG levels can help assess immune function and response to treatments targeting B cells."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 15, 2026Editorial policy

Key facts at a glance

LOINC
49841-0
Short code
CD19IGM
Synonyms
CD19+IgM+ cells NFr Spec
Category
chemistry
Sample
serum
Container
EDTA (purple top) anticoagulant tube; ACD (yellow top) tube is also acceptable. Heparinized tubes should be avoided as heparin may interfere with flow cytometric analysis.
Units
N/A
Ref low
5
Ref high
20
Fasting
false
Population
adult
Sex
all
Age range
0–99 years
Method
Flow cytometry using fluorescently labeled monoclonal antibodies against CD19 and surface IgM, with enumeration via multiparameter immunophenotyping
CPT
86355
SNOMED
444060000
Specimen volume
3-5 mL whole blood for adults; 1-2 mL for pediatric patients. Minimum 1 mL required for analysis.
Stability
Specimen should be processed within 24-48 hours of collection when stored at room temperature (18-22°C). Do not refrigerate. Viability and surface marker expression may decline beyond 48 hours.
Hemolysis max
100
Lipemia max
100
Icterus max
50
TAT
24–72 hours
Order
routine

Why This Test Is Done

Doctors may order this test to evaluate immune function, especially in conditions where B cells are affected, such as certain autoimmune diseases, infections, or before starting treatments like chemotherapy or monoclonal antibodies (e.g., for lymphoma or autoimmune disorders). It can also help monitor how well your immune system is responding to treatment.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample, usually drawn from your arm. The test involves a small needle, and you may feel a brief pinch. If you’re on blood-thinning medication, let your doctor know before the test.

What the Test Results Mean

Results show the concentration of IgG produced by B cells (CD19+ cells). While specific reference ranges vary by lab, lower levels may indicate immune deficiency or reduced B-cell activity, while higher levels might suggest overactivity or certain immune conditions. Your doctor will interpret results in the context of your overall health and medical history.

Common Conditions Monitored

This test is often used in diagnosing or managing conditions like chronic lymphocytic leukemia (CLL), autoimmune diseases (e.g., rheumatoid arthritis), or immune deficiencies. It may also be part of monitoring for infections or evaluating responses to treatments that target B cells.

Reference range

Reference values for CD19+IgM+ B-lymphocytes vary by age and laboratory. Results are typically reported as both percentage of total lymphocytes and absolute count. Adult reference ranges commonly used: CD19+ B cells 5-20% of lymphocytes; CD19+IgM+ (naive B cells) 40-70% of total B cells. Pediatric values differ and should be interpreted using age-matched reference intervals.N/A

Specimen: serum

No special patient preparation required. Recent vaccinations, infections, or immunosuppressive therapy may affect B-cell subset distribution and should be noted on the requisition. Specimen should be processed within 24 hours of collection for optimal viability.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: B-Cell Immunoglobulin G Levels

Short name

CD19+ IgG Levels

Frequently asked questions

What does a low level of CD19+ IgG mean?
A low level of CD19+ IgG may suggest an immune system that isn’t producing enough antibodies from B cells, which could increase your risk of infections. This might be seen in conditions like primary immunodeficiency, certain cancers (e.g., CLL), or after treatments that suppress the immune system.
How might abnormal IgG levels affect my treatment?
If your IgG levels are low, your doctor may adjust treatments to support your immune system, such as adding immunoglobulin therapy or modifying medications that target B cells. If levels are high, further evaluation might be needed to rule out conditions like monoclonal gammopathy or autoimmune disorders.
Can this test be used to track my immune response over time?
Yes, this test can help track how your immune system’s B cells are functioning over time. Repeated tests can show whether treatments are working, whether your immune system is recovering, or if you need adjustments to your care plan.
  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 15, 2026. · Read our editorial policy