Flow cytometry, is a method of sorting and measuring types of cells by fluorescent labeling of markers on the surface of the cells. It is sometimes referred to as FACS (Fluorescent Activated Cell Sorting) analysis.
Flow cytometric analysis is most often clinically used to help determine the type of leukemia or lymphoma a patient has and to assess the prognosis. Flow cytometry is quite sensitive; it is able to detect rare cell types and residual levels of disease.
Drugs, such as steroids, that suppress the immune system will affect the number of white blood cells in the patient's sample.
The physician will select a sample based on the type of cancer the patient is thought to have. In the case of lymphoma, the sample may be collected by fine needle aspiration biopsy, then the tissue sample will be separated into single cells. Analysis of leukemia will require a patient to give a blood sample. The patient's blood sample will be separated and the red blood cells removed. The sample will be mixed with a variety of different antibodies that can interact with markers on the surface of the cells. Different types of cells have characteristic markers on their cell surfaces, so a particular cell type can be identified by the antibodies that bind to it. The antibodies are labeled so that they will give off fluorescent light (glow) as they pass through the laser beam in the cytometer. The cytometer also measures the size of the cell and some information about the interior of the cell. The physician uses this information to determine the specific type of leukemia, such as myelogenous or lymphocytic, which in turn, helps to determine the type of treatment that will be best suited to the patient.
Sample analysis may also be performed using a more complex type of flow cytometer combined with a microscope, called a laser-scanning cytometer. This instrument is similar to a regular flow cytometer, but is better able to analyze solid tumor samples.
Flow cytometry is usually performed on blood, body fluids, or bone marrow. In most cases, no special preparation is required. If bone marrow aspiration is necessary or a biopsy is required from a solid tumor, the patient should be appropriately prepared for these procedures. However, the flow cytometry itself does not require any additional preparation on the part of the patient.
Aftercare and Risks
The only aftercare and risks associated with flow cytometric analysis are those associated with the sample collection procedure. The cell analysis itself requires no effort or risk from the patient.
A normal result will indicate that there is no increase in the number of any particular type of immune cell. The pathologist will see several different types of cells, but no one type will be present in increased numbers.
If the results are abnormal, the pathologist will observe an unusually large number of one particular cell type. The types of marker present on the cell will give further information about the type of leukemia or lymphoma and may indicate the patient's prognosis. For example, leukemic cells that have markers that are normally found on less mature cell types may suggest a poorer prognosis, and therefore more aggressive therapy may be recommended.
See Also Tumor grading
Javois, Lorette C. Immunocytochemical Methods and Protocols Totowa, NJ: Humana Press, 1999.
Rew, David A. et al. "Laser-scanning Cytometry." In The Lancet 353: (23 January 1999): 255-56.
Rosen, Shara, "Flow Cytometry: an Underexploited Diagnostic Power." Medical Laboratory Observer 30 (March 1998): 52-58.
"FACS Laboratory." Imperial Cancer Research Fund <http://www.icnet.uk> 5 July 2001.
"Flow Cytometry Core Educational Links." University of Florida <http://www.biotech.ufl.edu/~fccl/flow_edu.html> 6 July 2001.
Racquel Baert, M.S.
—A protein formed by the immune system (white blood cells) which reacts with a specific antigen.
—An instrument that measures cells.
—Light absorbed at one wavelength and emitted at another. That is, it glows.
QUESTIONS TO ASK THE DOCTOR
- What type of information do you expect to learn from this test?
- Are there any alternatives to doing this test?
- Are there any risks or complications?
- Are there any special preparations required?
- Is it possible that the test may give unclear or inaccurate results?
- Is this the best way to tell if, or what type of cancer I have?