Can Blood Tests Detect Cancer?

Blood Test specimens in test tubes sit in a lab.

Blood tests can reveal a wealth of information about our health. They are used to diagnose, track, and monitor many ailments. However, other than in rare occasions, blood tests alone can’t definitively tell you if you have cancer or not. At the same time, the results can lead your doctor to further appropriate testing which can lead to a diagnosis. Let’s look at some of the information blood tests can reveal in relation to discovering and diagnosing cancer.

Routine Blood Tests for Cancer Detection

Though quite common, routine blood tests provide valuable information when checking for cancer. A “CBC” or Complete Blood Count is a good starting point. This is a common blood test that measures different components in your blood. It includes several tests to measure and assess your red blood cells, white blood cells, and platelets. Below are specific metrics measured in the CBC test that provide clues related to a cancer diagnosis.

Platelet levels and how they can relate to cancer

One metric that can act as a warning sign for cancers is an MPV (Mean Platelet Volume) blood test. This test measures the average size of your blood platelets. Platelets are cells that exist in blood to form clots to heal a cut or wound, or to repair broken blood vessels. When you have too few platelets, this means that your body is not producing enough of them. There can be several potential reasons for this, but cancer is among them. Conversely, when you have too many platelets, this could also be related to cancer. It’s important to note that there are other possible reasons for unusual platelet levels. Your doctor will use the information from your test results to decide what next steps and tests can be used to arrive at a diagnosis. Read more about the MPV blood test here.

White blood cell counts and how they can relate to cancer

A WBC count (or “white blood cell” count) measures the amount of white blood cells in your blood. These cells are integral to your immune function. If your white blood cell count is too high, further testing may be ordered. If the blood test is being administered to check for signs of cancer, a high white blood cell count could point to leukemia. Of course, there are other reasons for a high white blood cell count, so this test is not definitive. On the flip side, if you have a lower-than-expected white blood cell count, this could be a sign of lymphoma. In either of these cases, your doctor will use the test results to plan further testing. A low or high white blood cell count doesn’t equal a diagnosis for cancer, but the cause requires further investigation.

Red blood cell counts and how they can relate to cancer

A RBC count (or “red blood cell” count) measures metrics related to your red blood cells. A low RBC count can in some cases indicate leukemia or lymphoma. This isn’t always the cause however—a low count can also signal anemia, or other disorders. On the other end of the spectrum, a high RBC count could indicate kidney tumors. A high RBC count can also be caused by non-cancerous ailments, such as dehydration or lung diseases. Checking various diagnostics related to your red blood cell counts can give your doctor clues that may point to certain cancers. Much like the other blood tests associated with diagnosing cancers, this test is just one of many that are used for an official diagnosis.

Blood tests for tumor markers

Tumor markers are substances that can be identified through lab testing. They can show up in blood testing, and also through analysis of tissue, stool, or urine. If tumor markers are counted in larger than usual numbers in the body, this may indicate that cancer is present. Tumor markers can be proteins, DNA changes, or gene expression patterns that present themselves in unusual amounts. Much like other blood tests for cancer, tumor markers alone are not enough for a diagnosis. If a higher-than-expected amount are present, your doctor will investigate further.

CA-125 blood test for cancer

One common blood test used to detect tumor markers for several cancers is the CA-125 test. This test checks how much of the cancer antigen 125 protein exists in a blood sample. Since some cancer cells contain this protein in higher amounts, it is a marker associated with certain cancers. As with other blood tests to detect cancer, the presence of this marker is used to gather information rather than provide a diagnosis. If your CA-125 test suggests that you have an elevated level of these proteins, your doctor will advise on further testing to determine the cause.

Blood tests for circulating tumor cells

A CTC blood test (or “circulating tumor cell” blood test) is a newer form of cancer blood testing. It looks for cells that have been shed from cancerous growths. These cells, once shed, circulate through the blood and can be tracked and traced with testing. Right now, CTC blood tests have proven useful in alerting doctors to potential cancers before other symptoms exist. They are also used in known cancer patients to track the progression or remission of cancers. At this time, the CTC blood test is used to diagnose breast cancer, prostate cancer, and colorectal cancer.

Blood testing for cancer

For the most part, blood tests alone can’t be used by themselves to diagnose cancer. At the same time, they provide a large amount of useful information to your doctor which can help with an eventual diagnosis. By studying specific clues and markers in your tests, your doctor can make informed decisions about the state of your health, and what it may mean for your treatment.

The bottom line

Blood tests can assist with diagnosing many ailments, including cancer. They provide invaluable information to doctors about the health of our bodies, ensuring we receive proper care. With over 3,500 tests available, Your Health Lab is proud to provide patients and doctors with the best diagnostics in the industry.


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