Flow Cytometry
Definition
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.
Purpose
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.
Precautions
Drugs, such as steroids, that suppress the immune system will affect the number of white blood cells in the patient's sample.
Description
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.
Preparation
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.
