Ordering Flow Cytometry: Tips, FAQs, Common Errors

September 14, 2023

When providers indicate “T-cell subsets” or “T-cell counts” (or other terms including “T-cell” without the words lymphoma, leukemia, neoplasia, or clonality), choose CD48 rather than TCELL. CD48 measures concentrations of helper and suppressor T-cells, and is often used when considering T-cell immunodeficiency, or in monitoring HIV. TCELL is an evaluation for neoplastic T-cell expansion, does not give T-cell concentrations, is a less common order, and is a much more expensive assay.

Similarly, “lymphocyte subsets”, “lymphocyte counts”, or related wording likely refers to TBNK, which gives concentrations for T-cells, B-cells, NK-cells, and also T-cell subsets (includes all values reported in CD48).  It is a comprehensive immune profiling of circulating lymphocytes and commonly used when screening for or evaluating immunodeficiency. Whereas TBNK gives absolute concentrations for B-cells, T-cells, and NK-cells, the tests named BCELL and TCELL are designed to see whether clonal (cancerous) expansion has taken place in either of those cell types.

If the provider is interested in flow cytometry for CLL, choose BCELL.

The panel previously called “Short B-cell” (SBCSF) is being discontinued as Warde switches to 12-color flow cytometry. Orders placed for SBCSF will be converted to BCELL, and this option will be removed on updated manual flow cytometry requisition forms.

Note that the ACUTE flow cytometry panel is not correct for CLL or hairy cell leukemia evaluations. However, ACUTE is useful when the provider is questioning an increase in monocytes. We often see ACUTE ordered incorrectly when there is an increase in lymphocytes. ACUTE is the correct order if there is an increase in blasts (or monocytes), when there is a history of acute leukemia, myelodysplastic syndrome, or a myeloproliferative neoplasm, or when there is a question of what kinds of cells are present (blasts versus lymphocytes, for example).

The most common valid reason for TCELL in peripheral blood is neutropenia or unexplained anemia with normal to high absolute lymphocyte count. Lymphopenia is rarely an indication for flow cytometry.

Cerebrospinal fluid flow cytometry collected for any reason other than acute leukemia or circulating blasts will generally be best ordered as BCELL. When there is a question of lymphoma involvement, unexplained mass, headaches, neurologic changes, or other presentations with no prior history of hematologic malignancy, the clinical question is usually whether lymphoma can be detected in CSF (most likely B-cell lymphoma). We see many CSFs ordered as ACUTE panels, which disrupts proper prioritization of specimens in the flow cytometry lab.

Please refer for Practice guideline #24 at https://www.ascp.org/content/docs/default-source/get-involved-pdfs/istp_choosingwisely/ascp-35-things-list_2020_final.pdf for additional guidance regarding flow cytometry. Always feel free to call Warde Client Services at (714)214-0300 for discussion with client representatives and/or Warde’s medical director prior to placing an order.