Flow Cytometry

What is flow cytometry?

Flow cytometry is a lab test used to analyze characteristics of cells or particles. During the process, a sample of cells or particles is first suspended in fluid. A lab technician treats the cells with fluorescent antibody dyes to label (or “tag”) specific proteins on the surface or inside of cells. This is called fluorescence-activated cell sorting (FACS). The cells are then injected into a flow cytometer machine. A computer can analyze and process approximately 10,000 cells in under a minute.

In medical settings, flow cytometry is used for:

• Cell counting.
• Cell sorting.
• Determining cell characteristics and function.
• Diagnosis and treatment of blood and bone marrow cancers.
• Finding biomarkers (a measurable substance whose presence might predict cancer behavior or response to treatment).
• Immunophenotyping (a way to classify cell types).

Lab technicians do flow cytometry and pathologists interpret the results. To run the test, they need a sample of your blood, bone marrow, tissue or other body fluid. The healthcare provider who requests the test (like your primary care physician or oncologist) takes a sample and sends it to the pathology lab for testing.

When is flow cytometry performed?

Healthcare providers use flow cytometry whenever they need to learn more about the cells inside your body. This type of testing can check the number and types of immune cells and identify and characterize cancer cells. Researchers can use flow cytometry to learn more about the complexities of things like:

• Blood cancers. This includes leukemia and lymphoma.
• Blood disorders. Paroxysmal nocturnal hemoglobinuria (PNH) and antithrombin deficiency are two examples.
• Immune function. Flow cytometry can test for conditions like HIV and inherited immune deficiencies.

Healthcare providers may also do flow cytometry as a follow-up test after a complete blood count (CBC). This is especially true if initial testing shows an increased number of lymphocytes, abnormal cell counts or the presence of immature blood cells.

Healthcare providers also use flow cytometry to diagnose and treat cancer. It can help predict how aggressive the disease will be and determine if the cancer will respond to certain treatments. It can also tell you if cancer has relapsed (returned) after treatment.

How does flow cytometry work?

Flow cytometry rapidly analyzes physical and chemical properties of cells and particles. Here’s how it works:

1. A lab technician places a sample of your blood, tissue or bone marrow in a suspension (liquid), treats the cell suspension with fluorescently tagged antibodies, and injects it into the flow cytometer.
2. The flow cytometer arranges the cells in a single file line, and then passes them in front of a laser beam, where they scatter light.
3. The flow cytometer counts and categorizes the cells based on how the laser beam scatters (bounces) off them.
4. Once the flow cytometer collects the data, it sends it to a computer.
5. A computer generates a report, usually a dot or bar graph.
6. A pathologist reviews the report and attaches a write-up of their findings to the test results.

What to expect with a flow cytometry test

Unless your healthcare provider gives you specific instructions, there’s usually no need to prepare before a flow cytometry test.

Your provider will need a blood, tissue or bone marrow sample. They can collect this during an appointment at their office. Once they have the sample, they’ll send it to a lab for testing.

Once the pathologist completes your flow cytometry test, they’ll analyze the data and send a report to your provider who ordered the test.

There are no known risks to having a flow cytometry test.

What type of results do I get and what do they mean?

It can take several days to a week to get your flow cytometry results, depending on the lab your healthcare provider uses.

The pathologist will look at the markers (antigens) on your cells. A healthy cell will have an antigen pattern that matches the type and maturity of the cell. An abnormal cell will show different patterns that could point to the presence of leukemia, lymphoma or other diseases.

When your provider receives your results, they’ll review the pathologist’s lab report, which is a summary of the raw data that they reviewed from the flow cytometer computer.

When interpreting your flow cytometry results, they’ll consider your symptoms, health history and most recent physical exam. They’ll share the results with you and help you understand what they mean. They’ll also use that information to determine your next steps.

Abnormal results could point to conditions like:

• Acute lymphoblastic leukemia.
• Acute myeloid leukemia.
• Chronic lymphocytic leukemia.
• Multiple myeloma.
• Non-Hodgkin lymphomas (both B-cell and T-cell).

If the results are abnormal, what are the next steps?

Your healthcare provider will talk with you about your flow cytometry results and possible treatment options. Your test results can tell your provider how aggressive your condition is, whether a certain treatment will work and how likely your condition is to relapse once you complete treatment. They’ll consider all these factors when coming up with a potential treatment plan.