What is the Difference Between PSA and Gleason Score

The key difference between PSA and Gleason score is that PSA is a blood test to diagnose prostate cancer by measuring the amount of prostate-specific antigen (PSA) in the blood, while Gleason score is a grading system to detect prostate cancer where the cells of the prostate gland are graded on a scale of 1 to 5. 

Prostate cancer is a cancer in the prostate gland, a small walnut-shaped gland found in males. Screening of prostate cancer can be done via different methods. PSA and Gleason score are two ways of screening or diagnosing prostate cancer.

CONTENTS

1. Overview and Key Difference
2. What is PSA  
3. What is Gleason Score
4. Similarities – PSA and Gleason Score
5. PSA vs. Gleason Score in Tabular Form
6. Summary – PSA vs. Gleason Score

What is PSA?

PSA is a blood test used to diagnose prostate cancer by measuring the amount of prostate-specific antigen (PSA) in the bloodstream. In this test, a blood sample is drawn from the vein in the arm and analyzed for PSA protein. PSA protein is a natural substance produced by the prostate gland. Usually, a small amount of PSA is present in the bloodstream. However, if PSA is higher than usual, it indicates prostate infection, inflammation, and enlargement of prostate cancer.

The normal PSA level of the blood is 4.0 ng/mL or lower. Increasing concentrations indicate problems with the prostate gland. However, it is possible for some individuals to have a PSA level below 4.0 ng/mL and still have cancer, while in others, the PSA level can fall between 4 and 10 ng/mL without indicating the presence of cancer. Therefore, doctors use other methods to improve the accuracy of the PSA test as a screening tool, such as measuring PSA velocity, percentage of free PSA, and PSA density. The risk factors involved in this test are swelling and redness in the area where the blood is drawn for evaluation in a laboratory.

What is Gleason Score?

The Gleason score is a scoring system used to grade prostate cancer. This score is based on the principle of how cancer cells look compared to healthy tissue when viewed under a microscope. Therefore, a prostate biopsy should be performed to determine the Gleason score. The less aggressive tumors generally look more like healthy prostate tissue. The more aggressive tumors look less similar to healthy prostate tissue and are likely to grow and spread to other parts of the body.

In this grading system, a pathologist examines how the cancer cells are arranged in a prostate gland and assigns a Gleason score from 2 different locations of the prostate gland. The lowest Gleason score is 6, which is a lower-grade cancer. The Gleason scores of 5 or lower are not used for cancer grading. Medium-grade cancer has a Gleason score of 7, while a Gleason score of 8, 9, and 10 is higher-grade prostate cancer. Furthermore, one of the risks associated with the Gleason score is that a prostate gland biopsy can occasionally result in excessive bleeding in patients.

What are the Similarities Between PSA and Gleason Score?

• PSA and Gleason scores can be used to screen or diagnose prostate cancer.
• Pathologists can perform both PSA and Gleason scores.
• Both are non-expensive methods to screen or diagnose prostate cancer.
• Some risks are involved while performing both PSA and Gleason scores.

What is the Difference Between PSA and Gleason Score?

PSA is a blood test used to diagnose prostate cancer by measuring the amount of prostate-specific antigen (PSA) in the blood. At the same time, the Gleason score is a grading system to detect prostate cancer where the prostate gland cells are graded on a scale of 1 to 5. Thus, this is the key difference between PSA and Gleason score. Furthermore, PSA is less accurate in detecting prostate cancer, while the Gleason score is more accurate in detecting prostate cancer.

The infographic below presents the differences between PSA and Gleason score in tabular form for side-by-side comparison.

Summary – PSA vs. Gleason Score

Prostate cancer develops when abnormal cells are formed in the men’s prostate gland. It usually develops very slowly over the years. The most commonly used tests to screen and diagnose prostate cancer are blood tests, a physical examination of your prostate, an MRI scan, and a biopsy. A common blood test to diagnose prostate cancer is PSA. It identifies the level of PSA antigen in the bloodstream. After a PSA test, doctors may go for a tissue biopsy and Gleason score to accurately determine the cancer and its aggressiveness. The Gleason score is a scoring system used to grade prostate cancer. So, this summarizes the difference between PSA and Gleason score.

Reference:

1. “Prostate-Specific Antigen (PSA) Test.” National Cancer Institute.
2.“Gleason Score and Grade Group.” Prostate Cancer Foundation.

Image Courtesy:

1. “Median prostate-specific antigen reduction across bicalutamide dosages and with castration” By Medgirl131 – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Micrograph of prostate cancer with Gleason score 8 (4+4) with fused glands with cytoplasmic vacuoles” By Jennifer Gordetsky and Jonathan Epstein – (CC BY 4.0) via Commons Wikimedia