## **Core Concept**
The Prostate-Specific Antigen (PSA) test is a widely used screening tool for prostate cancer. PSA is a protein produced by the prostate gland, and elevated levels can indicate prostate cancer, prostatitis, or benign prostatic hyperplasia (BPH). The normal range for PSA levels is crucial for interpreting test results.

## **Why the Correct Answer is Right**
The correct answer, ** 10 ng/mL - This option is incorrect because a level of > 10 ng/mL is considered elevated and warrants further investigation for prostate cancer.
- **Option B:** 4-10 ng/mL - This option is incorrect because while levels in this range may not immediately indicate cancer, they are considered gray zone or intermediate and may require further evaluation, such as a biopsy.
- **Option D:** > 20 ng/mL - This option is incorrect because a level of > 20 ng/mL is highly suggestive of prostate cancer and not within the normal range.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the normal range for PSA can slightly vary by laboratory but is generally considered to be < 4 ng/mL. Additionally, factors such as age, prostate volume, and the presence of certain medications can influence PSA levels, and thus, the interpretation of PSA results should be individualized. ## **Correct Answer:** . < 4 ng/mL