What types of lab tests are used in cancer diagnosis and treatment?
There are too many different kinds to list. But the complete blood count (CBC) is probably the most common lab test performed. It measures three main things:
Red blood cells (RBC): The number and quality of red blood cells can indicate if you’re anemic, which could be a sign of either iron deficiency or a blood cancer, such as multiple myeloma.
White blood cells (WBC): The number and type of white blood cells can show if you’re fighting off an infection, or if you have a blood cancer such as leukemia or lymphoma.
Platelets: The number of platelets can reveal conditions such as thrombocytopenia and thrombocytosis. Thrombocytopenia happens when your body generates too few platelets. It could be caused by a bone marrow disorder, such as myelodysplastic syndrome. Thrombocytosis happens when your body generates too many platelets, and could be caused by lung cancer or colorectal cancer.
What are the reference ranges for?
Reference ranges are designed to give people an idea of what normal values are for those categories. They’re created by averaging the results of large numbers of healthy individuals.
Ranges can vary even among labs and may be influenced by age, gender, or other physiologic conditions. But the general idea is that 95% of people tested will fall within those parameters.
It’s important to note that even if a value falls outside the normal range, it can still be due to a benign condition. And a value that falls within a reference range can sometimes be a sign of disease.
What other lab tests are used in cancer care?
Since a number of chemotherapy drugs and other cancer treatments can affect the liver and kidneys, a comprehensive metabolic panel (CMP) might be ordered before treatment begins to establish a good baseline for those organs. It might also be ordered several times during and after treatment to make sure they’re still functioning well.
CMPs measure enzymes and other aspects of blood chemistry that can indicate how well someone’s organs are functioning. BUN, for instance, stands for “blood urea nitrogen,” and is one of the things doctors look at to assess kidney function. The other is creatinine.
Doctors look at six different values to gauge liver function:
alanine aminotransferase (ALT)
aspartate aminotransferase (AST)
How does lab testing for tumor markers work, and what are some of the most common?
Scientists can now detect many substances made by cancer cells or produced by their hosts in response to the presence of a tumor. These might be found in the tumors themselves, or in the blood, bone marrow, lymph nodes or other tissues.
Lab tests may be used either to confirm the presence or absence of these substances (qualitative tests) or to determine the amount of these substances present in any given sample (quantitative tests).
Here are some of the most common cancers we test for, and their respective markers:
Is there any reason other than cancer that someone’s lab test results might be abnormal or show one of these markers?
Yes. Sometimes markers are not 100% specific for a particular malignancy. And those values could be elevated due to a totally benign condition.
PSA levels, for instance, might be elevated due to inflammation or enlargement of the prostate. This is a condition called benign hyperplasia. Endometriosis could be what’s causing an elevated CA-125 level. And benign bile duct and gallbladder diseases could be causing an elevated CA 19-9 level.
Similarly, when a comprehensive metabolic panel shows the amount of creatinine increasing in someone’s blood or decreasing in someone’s urine, it could indicate a problem because the body is not eliminating it. But it could also mean that someone is just dehydrated.
That’s why it’s very important to take the information and put it into context. Your doctor looks at the full picture — including your physical examination and medical history — before deciding if any abnormal value is cause for concern.
Is there anything else that can affect lab test results?
Absolutely. Results could be impacted by the season, whether or not you’re fasting, even your posture during the sample retrieval process. They might also be affected by how a sample is handled, prepared or processed after it’s obtained.
At MD Anderson, we ensure the accuracy of every lab test by having the results reviewed and verified by an in-house technologist or pathologist before they’re released.
Anything else you want people to know about lab tests?
Lab tests are evolving. We’ve gone from using lab tests to identify patients with particular diseases to predicting who will be the most likely to respond well to certain types of therapy: essentially, it’s personalized medicine.
I fully expect this trend to continue, too, as we move more toward disease prevention than selective treatment. Over time, it will completely transform the scope of laboratory medicine.