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How Does Blood Test Help to Detect Cancer

Published on Mar 15, 2021 and last reviewed on Nov 19, 2021   -  3 min read


Blood tests are very useful in diagnosing various physiological and pathologic conditions, including cancer. This article explains the usefulness of a blood test for the detection of cancer.

How Does Blood Test Help to Detect Cancer


Cancer is a malignant neoplastic disease that can cause serious complications if not diagnosed and managed early. Various tests can be helpful to diagnose it. The blood test is one of such beneficial tests. When you suspect something different with your body and your physician suspects any cancer possibility, various tests will be performed to confirm the diagnosis. It can be either blood tests or other laboratory tests like urine analysis (exfoliative cytology) or conducting a biopsy of the affected area. Blood tests are best suitable for blood cancers which are called leukemia, but they are of little help in various other types of cancers. Anyway, these blood tests can help the physician in understanding the functioning of the body. It is important to understand that mere referral for blood tests does not indicate cancer.

What Are The Other Uses Of Blood Tests?

Blood tests are usually done to check various levels of components of blood, proteins, various antigens, etc. Some of the basic things that are checked are red blood cells, white blood cells, platelets, immunoglobulins, blood type, blood sugar levels, proteins, etc. All these measurements of various components of blood are specific for normal individuals. Any increase or decrease in the levels can be physiologic or pathologic and needs a detailed assessment to diagnose. Blood tests are helpful in the diagnosis of infections, diabetes, hyperlipidemia, thrombocytopenia, etc.

What Does A Blood Test For Cancer Show?

Samples are collected by the physician or technician and sent to the laboratory to analyze the samples for any signs of cancer. There can be cancerous cells, proteins, or any other product produced by the cancer cells in the sample. Also, as mentioned above, a blood test will help your physician to understand the functioning of your body and whether there is an effect caused by cancer or not.

Following are some of the blood tests that can be performed:

1.Complete Blood Count (CBC):

This is a various basic test performed for any condition and as a routine too. CBC tests mainly include Total WBC count, differential WBC count, Platelet count, RBC count, HB level, Blood indices, and various other tests. CBC test with peripheral smear examination report is helpful in the diagnosis of leukemia, especially AML, CML, CLL, ALL, Polycythemia vera, etc.

2. Testing of Blood Protein:

Serum Protein Immunofixation electrophoresis is diagnostic for Multiple myeloma like plasma cell dyscrasia blood cancers. However, a bone marrow study also needs to be done to predict prognosis and confirmation of diagnosis.

3. Tumor Marker Tests:

These are the chemicals that are produced by the cancer cells and are detectable in the blood. It is important to understand that various tumor markers are also produced by normal cells of the body. The levels can also be elevated in a non-cancerous condition. Hence, tumor markers alone cannot be used to diagnose cancer, and multiple diagnostic tests must be carried out. There are certain tumor markers specific for certain cancers like prostate-specific antigen (PSA) for prostate cancer, cancer antigen 125 (CA 125) for ovarian cancer, alpha-fetoprotein (AFP) for liver cancer, calcitonin for medullary thyroid cancer, and human chorionic gonadotropin (HCG) for germ cell tumors, such as testicular and ovarian cancer, etc.

4. Circulating Tumor Cell Tests:

The advances in the medical field and cancer diagnosis have brought forward certain blood tests to determine cells that have got detached from the site of primary cancer and are present in the bloodstream. One such circulating tumor cell test approved by the Food and Drug Administration for monitoring people suffering from breast, colorectal, or prostate cancer is not frequently being used in a clinical setting.

What Do The Results Indicate?

The physician or specialist interprets the test results. Test interpretation must be made very carefully as the outcomes can be due to various other factors like any other non-cancerous condition, physiology of the body, etc. In some conditions, non-cancerous conditions can give abnormal results, and the correct diagnosis must be made to manage the condition. Also, in a few cases, normal blood tests may be seen even though cancer is there. Finally, your physician, specialist, pathologist, etc., decide the diagnosis and treatment plan depending on the clinical scenario, medical history, and test results.

What To Expect After Interpretation Of Tests?

After the interpretation of the blood tests and another test like urine test has been done, certain other definitive tests must also be done before concluding the condition. Some of them are biopsy which can be excisional, incisional, wedge biopsy, etc. A biopsy is a process of obtaining cancerous cells with or without normal cells surrounding it using surgical procedures to check for the type of cells present in the affected site. This helps in making a definitive diagnosis.

In a few patients, the tumor markers can be checked at regular intervals. This testing will be done during your regular follow-ups, and this helps in checking your response to treatment and progression of the disease (cancer). After a definitive diagnosis is made, your specialist will decide the treatment, which may include surgery, chemotherapy, radiotherapy, or a combination of these. Certain other new treatments may be included. Blood tests are not usually useful to check the prognosis for relapse of cancer.


Blood tests are usually done to check for various conditions and as a routine check-up. These tests can also be helpful in the diagnosis of cancer. Although it cannot be used alone for diagnosis, it aids in the diagnosis process. Detailed information is required to understand these tests. Online medical platforms have made these consultation processes very easy by connecting the specialist and patient digitally. Consult a specialist using these platforms to know more about these tests.

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Last reviewed at:
19 Nov 2021  -  3 min read




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