To understand the purpose of a tumor marker test, it is important to understand exactly what tumor markers are. The tumor markers are a group of proteins, hormones, enzymes and receptors as well as other substances present in cells that are produced in exaggerated amounts because of the presence of malignant cells within the body. For the purpose of medical examination, it helps to know that tumor markers are naturally present in the blood, urine as well as the actual tumor. It also helps to know that some tumor markers are specific to a certain type of cancer rather than being generic. As a result, a tumor marker blood test is most often used in the diagnosis of suspected cancer as well as monitoring of the condition. Tumor marker blood tests are also commonly used in order to monitor the reoccurrence of a tumor after successful treatment or removal of the initial tumor. However, tumor marker tests are in no way a definite method of diagnosing cancer as there is an infrequent occurrence where they are present in large amounts in people that are not suffering from cancer.
As with any other type of blood test, a tumor marker blood test will require a sample of some amount of blood being withdrawn from the body with the help of a syringe penetrating the vein located just behind the arm. First, the site where the injection will break the skin will be cleaned thoroughly and a strap will be fastened to the top of the arm. This will cause the vein to swell up and become more prominent – making it easier for the doctor to penetrate the vein correctly and without any complications. Once the syringe has been filled with the required amount of sample blood, the needle is withdrawn and drained into a marked test tube. This is then sealed and sent to the laboratory for analysis. The lab results will usually be sent back to the presiding doctor within a few hours for him or her to draft a more informed opinion of the condition and provide the best possible treatment.
Since false positives are such a common occurrence, it is essential for a physician to correlate the test results of a tumor marker test with results of some other medical tests such as tissue biopsies and other procedures. Most false positives will occur when a patient has cross reacting antibodies that tend to interfere with the test.