Advanced Diagnostic Laboratories

CD20 + B Cell Enumeration Assay

Test Code

CD20

Description

CD19 and CD20 are both B cell receptors that play a central role in cell maturation and function. CD19 is expressed at all stages of B cell maturation and thus is the preferred marker for lymphocyte phenotyping assays. The exact biological function of CD20 is not known. It may be involved in the regulation of activation, proliferation and differentiation of B cells. Its expression is more variable than CD19 and is increased following activation.

Patients with autoimmune diseases or cancer who are being treated with drugs like rituximab, which destroy CD20+ B cells, may benefit from flow cytometric detection of residual CD20+ B cells as an indication of treatment efficacy. This assay may be insufficiently sensitive to detect minimal residual disease (MRD) following chemotherapy for malignancy.

Collect

Draw one green top (sodium or lithium heparin), lavender top (EDTA) or ACD (acid citrate dextrose) vacutainer tube.

Please Note: For absolute counts, a complete blood count (CBC) is also required, so an additional EDTA lavender tube should also be submitted. Alternatively, CBC results from a blood collection within 3 days of the phenotyping blood collection can be submitted.

Patient Prep

Handling: Do not centrifuge! Keep at room temp (18-22°C).

Preferred volume: 4 mL

Pediatric Collection

Minimum volume: 1mL blood

Unacceptable Conditions

Frozen, clotted, hemolyzed, spun down, citrate anticoagulant (blue top), past stability

Storage Transport Temp

Maintain and transport specimens at room temperature (18-22°C).
Ship specimens Priority Overnight via Fed Ex in container sufficiently insulated to avoid temperature extremes (<10°C and >37°C).

Stability

48 hours at room temperature (18-22°C).

Notes

CBC with Differential results from within 3 days of draw must also be provided or a lavender top included with required specimen to run CBC at ADx.
Samples are accepted Monday through noon on Fridays.

Performed

Tuesday - Friday

Samples accepted Monday through noon on Friday

Methodology

Flow Cytometry

Turnaround Time

2-4 business days

Department

Immunology Lab - Phenotyping Assays

Synonyms

B Cell Enumeration, CD20 B Cells, Flow Cytometry (CD20), B Cell Marker;CD20M

Study Offerings

CAP/CLIA

Reference Interval

Lymphocyte Subset Normal Range Chart

Interpretation

This test is useful for assessing B Cell percentages and numbers and assists in the evaluation of humoral immunodeficiences. It is also useful for monitoring depletion of CD20 B cells following anti-CD20 monoclonal (e.g. Rituximab) therapy. Sensitivity threshold is 1% of lymphocytes, which may be insufficient for the detetion of minimal residual disease (MRD) following chemotherapy for malignancy.