Ordering Recommendation

Use to enumerate B cells in peripheral blood or monitor response to rituximab therapy in patients with autoimmune disorders. To evaluate for primary B-cell deficiency (eg, agammaglobulinemia, common variable immunodeficiency [CVID], hypogammaglobulinemia), order B Cell Subset Analysis (3002216).

New York DOH Approval Status

This test is New York state approved.

Specimen Required

Patient Preparation

Green (sodium heparin). Also acceptable: lavender (EDTA) or pink (K2EDTA).

Specimen Preparation

Transport 5 mL whole blood. (Min: 1 mL). Do not freeze.

Storage/Transport Temperature

Preferred transport temp: Room temperature. Also acceptable: Refrigerated. Specimen should be received within 72 hours ofcollection for optimal viable testing.

Unacceptable Conditions

Clotted, hemolyzed, or frozen specimens. Specimens received more than 72 hours from collection.


Clinical history, differential diagnosis, and any relevant pathology reports.


Ambient: 72 hours; Refrigerated: 72 hours; Frozen: Unacceptable.


Flow Cytometry




1-2 days

Reference Interval

Refer to report.

Interpretive Data

Compliance Category

Laboratory Developed Test (LDT)


Monoclonal antibody-based therapies, such as rituximab that target the CD20 antigen, are being used to treat patients with avariety of autoimmune disorders. The effectiveness of this therapy is dependent on the degree of B-cell suppression andvaries by disease state. This assay is designed to detect low levels of B cells and provide quantitative cell numbers in thesetting of rituximab-treated patients using both CD20 and CD19.

Hotline History


CPT Codes

86355; 86356


Component Test Code* Component Chart Name LOINC
3016432 CD19+ Percent of Lymphocytes 8117-4
3016433 CD19+ Count of Lymphocytes 8116-6
3016434 CD20+ Percent of CD19+ Cells 94689-7
3016435 CD20+ Count of CD19+ Cells 9558-8
3016436 Cell Viability 33193-4
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.


  • B cell depletion
  • CD19
  • CD20 on B Cells
  • high sensitivity B cell count
  • Kesimpta monitoring
  • Obinutuzumab
  • Ocrelizumab
  • Ocrevus monitoring
  • Ofatumumab
  • Rituxan monitoring
  • Rituximab
  • Veltuzumab
B-Cell CD20 Expression by Flow Cytometry, Quantitative