The next level of the diagnostic process involves a laboratory analysis of blood samples. Two categories of blood tests are used to help in the diagnosis of cancer.
Non-Specific Tests Most blood tests are non-specific. This means they can reveal an abnormality in the blood that indicates some illness, but not which one.
A blood count, for example, may show anemia . Why would you be anemic? Lots of reasons, including cancer. But the anemia may not be related to a tumor unless you have a history of bleeding in the bowel and x-rays show a cancer of the colon. Similarly, there are tests for liver function that indicate abnormalities in that organ. But the problem might be caused by gallstones, hepatitis, tumors or drug toxicity. Certain patterns in the test results will suggest tumors or some other cause of bile obstruction. Other patterns suggest hepatitis. But essentially these patterns are only important clues. They are not solutions to diagnostic questions.
There are so many tests used to detect abnormalities in different organ systems that physicians usually obtain a whole panel of them—blood counts, tests of metabolism (including levels of minerals such as calcium) and tests for the liver, kidneys or thyroid. The test results may suggest certain types of tumors, but no specific diagnosis can be made on the basis of these tests alone.
Specific Tests Other blood tests are fairly specific for particular kinds of cancer, often
several kinds. These tests will be ordered if your doctor strongly suspects one of these cancers.
