Carcinoembryonic Antigen Test
The carcinoembryonic antigen (CEA) test is performed to measure the level of a protein that is associated with cancer. Also called a tumor marker, CEA can help detect the presence of cancer.
The carcinoembryonic antigen is a protein on the cell surface of certain types of cancer cells and is usually present in the blood and other body fluids such as the pleural fluid around the lungs, peritoneal fluid in the abdomen and cerebrospinal fluid around the spine. The CEA test is commonly performed using a blood sample. However, it can also be performed on the body fluids mentioned earlier.
The CEA test can help in the diagnosis of various types of cancer though it is only a supportive test and more definitive diagnostic tests such as imaging scans need to be performed. CEA is produced in cancer of the following:
- Colon and rectum
Your doctor may order this test if you have symptoms of these cancers, and during and after treatment to monitor its effectiveness.
The CEA test is not performed as a screening test for cancer, but it can help determine:
- The prognosis or outcome of the cancer
- How effective cancer treatment has been and
- If there is a recurrence of the cancer
Preparation for the procedure
No special preparation is necessary for a CEA blood test. You may have to empty your bowels and bladder if CEA is tested using peritoneal fluid. Inform your doctor if you are a smoker as smoking may result in increased CEA levels. You will be advised to avoid smoking for a period of time before the test.
The procedure usually involves obtaining a sample of blood from a vein in your arm. An elastic band may be tied around your arm to help make the veins more pronounced. The skin over the site is cleaned with an antiseptic. A needle is inserted into a vein and the blood is drawn into a syringe, test tube or vial. You may feel a slight sting as the needle is inserted.
Depending on the location and type of the tumor, your doctor may require CEA testing of other body fluids such as cerebrospinal fluid, pleural fluid, or peritoneal fluid.
To obtain cerebrospinal fluid, you may be in a seated position or asked to lie on your side with your knees drawn up. A local anesthetic is administered over an area in your lower spine and a needle is then inserted between two vertebral bones to enter the spinal canal. A small amount of spinal fluid is drawn into a syringe.
If pleural fluid is to be obtained, ultrasound imaging may be used to guide the needle to the correct location within the chest cavity to draw the fluid that surrounds the outside of each lung.
If peritoneal fluid is to be obtained, ultrasound imaging may be used to guide the needle to the correct location to draw the fluid that lines the abdominal wall.
The collected sample is then sent to the laboratory for evaluation. The results will be available in a few days.
The CEA test is usually a simple and uneventful procedure with minimal risks. The risks vary depending on whether blood or another type of fluid was drawn for the test. These include:
- Pain which may be relieved with a cold pack
- Difficulty obtaining blood
- Pain and soreness in the back if cerebrospinal fluid is drawn
- Headaches if cerebrospinal fluid is drawn
- Lung injury or infection and blood loss if pleural fluid is drawn
- Lightheadedness and damage to the bowel or bladder leading to infection if peritoneal fluid is drawn.
Interpreting the Results
Your doctor will compare your CEA levels with previous test results if any.
Healthy people normally have less than 3 nanograms of CEA per mL of blood (ng/mL). Following successful cancer treatment it may take 1-3 months for your CEA levels to come down to this range. If the levels are still high, it may indicate that treatment is not working. If the levels were low before and are now raised it can indicate that the cancer has come back.
Having elevated CEA levels does not necessarily mean you have cancer. CEA levels may be elevated in chronic smokers and in cases of infection, cirrhosis, stomach ulcers and inflammatory bowel disease. CEA is also produced by a growing fetus in the womb and its levels are elevated during pregnancy. Your doctor will perform other tests to confirm the diagnosis.
The carcinoembryonic antigen test is a useful test in the diagnosis and prognosis of certain types of cancer. Your doctor may recommend this test along with other tests such as imaging studies to see how well the cancer is responding to treatment or if the cancer has returned after a period of remission.