What Is Flow Cytometry?
Flow cytometry is a way to look closely at the features of cells or particles. A sample of blood or tissue goes into a machine called a cytometer. In less than a minute, a computer can analyze thousands of cells.
A flow cytometry blood test can be part of the process of diagnosing certain diseases, including blood cancers such as leukemia or lymphoma. Scientists also use flow cytometry in medical research.
What Does a Flow Cytometry Test Show?
A flow cytometry test can show doctors many pieces of information. It can help them:
- Count cells
- Sort cells
- Look at the functions and features of cells
- Find microorganisms such as bacteria, yeast, or fungi
Why Would a Doctor Order a Flow Cytometry Test?
Usually, your doctor will order a flow cytometry blood test as a follow-up to a complete blood count or white blood cell scan. If these tests show something unusual, such as a high number of white blood cells called lymphocytes or undeveloped blood cells, flow cytometry can give them a better picture of what's happening in your body.
When Is Flow Cytometry Performed?
Doctors often perform a flow cytometry test while diagnosing blood cancers and immune system diseases. It can tell your doctor exactly which type of leukemia or lymphoma you have, and help them figure out how serious the cancer might be and whether it will respond well to a certain treatment.
"The first thing it tells us is 'Are the cells normal or not?' then, 'Are they lymphoid or myeloid?'" says Michael Andreeff, MD, PhD, professor of medicine in the Department of Leukemia, Division of Cancer Medicine, at the University of Texas MD Anderson Cancer Center in Houston, Texas, and one of the early developers of flow cytometry.
Beyond that most basic information, Andreeff says a flow cytometry test can show 20-30 different features on each cell.
Your health care team may also use flow cytometry after you're diagnosed. It can help you decide when it's time to start treatment and show whether the treatment is working. After your treatment is finished, a flow cytometry test can be part of your regular follow-up testing to see whether a disease has come back (or relapsed).
"That's where flow cytometry really shines," Andreeff says. He calls it the most valuable kind of test for finding very small amounts of cancer that may be left behind after treatment, known as minimal residual disease (MRD). "It can detect one in 1,000 or one in 10,000 malignant cells."
Detecting MRD is very important in deciding whether you need more treatment or a different type of treatment.
Flow cytometry isn't just for cancer. Your doctor might use it any time they need to look more closely at your cells. For example, they can study your DNA or see how your body reacts to a vaccine or treatment for an immune condition.
How Does Flow Cytometry Work?
Flow cytometry works by exposing cells or particles to light from different kinds of lasers. The way the light passes through or bounces off of the cells reveals details about their size, shape, and makeup.
For example, the light will behave differently depending on how large a cell is, what the surface of the cell looks like, and how many small particles are inside the cell. That can show what kind of cell it is.
How Do Doctors Perform Flow Cytometry?
A flow cytometry test starts with either a blood sample or a sample of your tissue or bone marrow that a doctor removes during a biopsy.
A lab worker mixes the sample into a special liquid that contains dyes and lab-made proteins called antibodies. The antibodies attach to targets on cells called antigens, causing those cells to light up with a specific color when they pass in front of the lasers. They inject this liquid into the flow cytometer machine.
The machine lines up the cells in single file and moves them past the light. A computer records data about the color, brightness, and pattern of the light as it interacts with each cell or particle. This takes place in a split second.
Then the computer organizes the information into a graph that shows how many cells in the sample share certain features. Depending on what they're looking for, the person running the test can filter the results for only certain information. That's called "gating."
What Are the Main Components of Flow Cytometry?
There are three main systems of a flow cytometry machine:
- Fluidics. This system moves cells or particles in a stream past the laser beam.
- Optics. This has lasers to light up the particles in the sample and create light signals.
- Electronics. This system converts light signals into electronic signals so a computer can process them.
Some machines also include a system that sorts particles so scientists can save them and study them further.
What Happens After Flow Cytometry?
After your test, a doctor called a pathologist will look at the results of your flow cytometry and create a lab report. They'll consider that data alongside your medical history, physical exam, and any symptoms, and give their opinion about whether you have a disease such as cancer.
Your doctor will talk to you about your results. They'll explain what they mean and help you understand the next steps. They'll give you all the details of your condition and go through treatment options, if that's needed.
Which Cancers Can Flow Cytometry Detect?
If you get results from a flow cytometry test that show cells that aren't normal, it might mean that you have a form of cancer. Flow cytometry is most often used to help diagnose blood cancers, including:
Which Diseases Can Flow Cytometry Detect?
Besides cancer, Andreeff says any disease that's diagnosed based on features of immune cells may involve a flow cytometry test.
It can help:
- Find when an HIV infection has caused AIDS
- See how well an HIV drug has worked
- Look closer at other infectious diseases, autoimmune disorders, or immunodeficiencies (when your body doesn't produce enough antibodies or cells to fight off germs)
Flow cytometry machines allow doctors to give you more personalized and accurate medical care. With this machine, your care team can find the best treatment option for your needs.
Takeaways
Flow cytometry is a method of testing cells or particles from a sample of blood, bone marrow, tissue, or other body fluid. It quickly studies thousands of cells and gives a detailed picture of what kind of cells are in the sample and how they're working. It's often used in diagnosing diseases and in medical research. You might have a flow cytometry blood test to help diagnose leukemia or lymphoma, and to check whether treatment is working.
Flow Cytometry FAQs
What is the application of flow cytometry in diagnosis?
Flow cytometry testing can be used to help diagnose any disease that involves immune cells. It can quickly pick out abnormal cells and identify exactly what is abnormal about them, which tells your doctor what condition you have.
Can flow cytometry detect autoimmune diseases?
Yes. With many autoimmune diseases, doctors see patterns of certain types of cells. Flow cytometry can identify these patterns to help diagnose diseases such as lupus, multiple sclerosis, and rheumatoid arthritis.
Can flow cytometry detect viruses?
Yes. Some flow cytometer machines can detect, analyze, and sort particles that are smaller than cells, including viruses. This process is called flow virometry.
