The main difference between total and free PSA is that total PSA (Prostate-Specific Antigen) includes both bound and free PSA circulating in the blood, whereas free PSA is the non-bound PSA circulating in the blood.
Total and free PSA are two types of PSA, a protein produced by the prostate gland cells. PSA circulates in the blood in two ways: bound PSA and non-Bound PSA.
Key Areas Covered
1. What is a Total PSA
– Definition, Features, Importance
2. What is a Free PSA
– Definition, Features, Importance
3. Similarities Between Total and Free PSA
– Outline of Common Features
4. Difference Between Total and Free PSA
– Comparison of Key Differences
Key Terms
Free PSA, Total PSA
What is a Total PSA
The total PSA is the total amount of PSA (prostate-specific antigen) that occurs in the blood. It includes the free PSA and the amount of PSA bound to the other proteins. PSA is a protein produced by both normal and malignant prostate gland cells. The PSA test measures the amount of PSA in the blood. The test results come in nanograms per milliliter of blood and measure the total PSA amount in the blood. The normal level of PSA in the blood is 4 to 10 ng/mL. Elevated levels of PSA occur in the blood in conditions like prostate cancer. Other than that, several benign conditions, inflammation in the prostate gland (prostatitis), and the enlargement of the prostate gland (benign prostatic hyperplasia (BPH)) can cause higher levels of PSA in the blood.
Figure 1: Prostate Gland
Furthermore, by estimating total PSA levels, the PSA test is important for the early detection of prostate cancer when there are no signs and symptoms of the disease, to check cancer when the signs of cancer are present, to plan to treat prostate cancer, monitor prostate cancer treatments, and to check the recurring of the prostate cancer after treatment. Furthermore, PSA tests are important when a person has an average risk of prostate cancer, age, and race with an increased risk of prostate cancer.
What is a Free PSA
Free PSA is the amount of PSA (prostate-specific antigen) that occurs in the blood, not binding to other proteins in the circulation. The free PSA test measures the PSA that does not bind to the other proteins in the circulation. These PSAs circulate freely in the bloodstream without binding to other proteins in the circulation. Comparing free to total PSA levels, doctors can get an idea about how likely a person has prostate cancer. For example, the higher ratio of free to total PSA indicates a low risk of prostate cancer. In comparison, the lower ratio of free to total PSA indicates a high risk of prostate cancer.
Figure 2: Free to Total PSA Ratio
Other factors affecting the PSA level in the blood include enlarged prostate glands, prostate stimulation, medications for enlarged prostate glands, vigorous exercise, urinary tract infections, prostate infections, prostate surgery, etc.
Similarities Between Total and Free PSA
- Total and free PSA are two measurements of PSA that occur in blood circulation.
- PSA is a protein produced by the prostate gland cells.
- They are important in measuring pathogenic conditions and cancer.
Difference Between Total and Free PSA
Definition
Total PSA refers to the total amount of prostate-specific antigen (PSA) in the blood, while free PSA refers to the amount of PSA in the blood that is not bound to other proteins.
PSA Levels
The normal total PSA level is 4-10 ng/mL in blood, while the normal free PSA level is 25%.
Occurrence
The total PSA includes bound and free PSA in the blood, while free PSA includes the unbound PSA with other proteins in the blood.
Conclusion
In brief, total and free PSA are the two methods of PSA occurring in the blood. Prostate-specific antigen (PSA) is a protein produced by the prostate gland cells. However, it circulates in the blood in two methods: free PSA and bound PSA into other proteins in the blood. Total PSA includes both the bound and free PSA in the blood. The normal level of total PSA in the blood is 4 to 10 ng/mL. In comparison, free PSA is the unbound PSA circulating in the blood. Also, the normal level of free PSA in the blood is 25%. Therefore, the main difference between total and free PSA is the concentration and the form in the blood.
References:
- Prostate-specific antigen (PSA) test. National Cancer Institute. (n.d.).
- MediLexicon International. (n.d.). Free PSA: Test, results, and prostate cancer. Medical News Today.
Image Courtesy:
- “Diagram showing T1-3 stages of prostate cancer CRUK 278” By Cancer Research UK – Own work (CC-BY SA 4.0) via Commons Wikimedia
- “Free psa table” By Ryanjo – Own Work (CC-BY SA 3.0) via Commons Wikimedia
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