PSA Blood Test: Prostate Cancer Screening & Results

What Is a PSA Blood Test?

A PSA blood test measures the level of prostate-specific antigen in your blood. PSA is a protein produced exclusively by the prostate gland. While small amounts of PSA normally enter the bloodstream, elevated levels may indicate prostate disease, including cancer, benign enlargement, or inflammation.

PSA stands for prostate-specific antigen, a protein manufactured by cells in the prostate gland. The primary function of PSA is to liquefy semen after ejaculation, helping sperm become more mobile. While most PSA remains in semen, a small amount enters the bloodstream, and this is what the PSA blood test measures.

The prostate gland is a walnut-sized organ located below the bladder and in front of the rectum in men. It surrounds the urethra, the tube that carries urine from the bladder out of the body. As men age, the prostate often enlarges, which can affect both urinary function and PSA levels.

Understanding PSA testing is crucial because it remains one of the primary tools for early detection of prostate cancer, which is the second most common cancer in men worldwide. However, the test has limitations—it cannot distinguish between cancer and other prostate conditions, making interpretation complex and often requiring additional testing.

Types of PSA in the Blood

PSA exists in two forms in the bloodstream: bound PSA (attached to proteins) and free PSA (unbound). The majority of PSA in blood is bound to proteins, while a smaller proportion circulates freely. The ratio of free to total PSA can provide additional diagnostic information.

When the free PSA percentage is low (below 10%), there is a higher probability that an elevated PSA is due to cancer. Conversely, a higher percentage of free PSA (above 25%) suggests benign prostatic hyperplasia (BPH) is more likely. This distinction helps doctors decide whether a biopsy is necessary.

When Should You Get a PSA Test?

PSA testing is generally recommended for men between ages 50 and 75 who wish to screen for prostate cancer. Men with hereditary risk (two or more close relatives with prostate cancer) should consider starting at age 40. Testing may also be recommended if you have urinary symptoms or your doctor detects prostate abnormalities during examination.

The decision to undergo PSA testing should be made after careful consideration of the potential benefits and risks. Several situations may warrant PSA testing:

Screening Without Symptoms

For men without symptoms, PSA testing is typically considered between ages 50 and 75. Before age 50, prostate cancer is relatively rare, occurring in fewer than 1 in 10,000 men annually. After age 75, the likelihood that a small, slow-growing prostate cancer detected by PSA alone will cause harm during a man's lifetime decreases significantly.

The rationale behind this age range is based on extensive research, including the European Randomized Study of Screening for Prostate Cancer (ERSPC), which demonstrated that PSA screening reduces prostate cancer mortality by approximately 20% in men aged 55-69. However, the same study also highlighted significant overdiagnosis—detecting cancers that would never have caused symptoms or death.

Symptoms Suggesting Prostate Problems

Your doctor may recommend a PSA test if you experience symptoms that could indicate prostate disease:

• Frequent urination: Especially at night (nocturia)
• Weak urine stream: Difficulty starting or maintaining flow
• Incomplete emptying: Feeling the bladder isn't fully emptied
• Blood in urine or semen: Requires prompt medical evaluation
• Pain or burning: During urination or ejaculation
• Pelvic discomfort: Persistent pain in the lower back, hips, or pelvis

These symptoms can result from various conditions, including benign prostatic hyperplasia, prostatitis, urinary tract infections, or prostate cancer. PSA testing, along with other examinations, helps determine the underlying cause.

Hereditary Risk Factors

Men with a strong family history of prostate cancer face significantly elevated risk and should consider earlier and more frequent screening. Hereditary risk is defined as having two or more first-degree relatives (father, brother, son) who have been diagnosed with prostate cancer, or having relatives who developed prostate cancer at an unusually young age (before 55).

For men with hereditary risk, screening is recommended starting at age 40, with testing every 1-2 years. Research shows that hereditary prostate cancer tends to occur earlier and may be more aggressive than sporadic cases, making early detection particularly valuable in this population.

Monitoring After Diagnosis or Treatment

If you have been diagnosed with prostate cancer or have completed treatment, regular PSA monitoring is essential. Following treatment (surgery, radiation, or other therapies), PSA levels should become very low or undetectable. Rising PSA levels after treatment may indicate cancer recurrence, prompting further evaluation and potentially additional treatment.

How Is the PSA Test Performed?

The PSA test is a simple blood draw from a vein in your arm. No special preparation is required—you can eat and drink normally. The blood sample is sent to a laboratory, and results are typically available within 1-4 days. Before the test, sit for a few minutes to allow fluid levels in your blood to stabilize.

The PSA blood test is straightforward and minimally invasive. Here's what to expect:

Before the Test

No fasting or special dietary restrictions are needed before a PSA test. However, certain activities can temporarily elevate PSA levels and should be avoided 48-72 hours before testing if possible:

• Ejaculation: Can temporarily increase PSA levels
• Vigorous cycling: Pressure on the prostate from bicycle seats can affect results
• Prostate examination (DRE): Should be done after PSA testing, not before
• Urinary tract procedures: Recent catheterization or cystoscopy may elevate PSA

If you have an active urinary tract infection, the PSA test should be postponed until the infection is treated and resolved, as infection can significantly elevate PSA levels.

During the Test

A healthcare professional will draw blood from a vein in your arm using a standard needle. The procedure takes only a few minutes. You may feel a brief pinch when the needle is inserted. After the blood is drawn, a small bandage is applied, and you can resume normal activities immediately.

After the Test

The blood sample is sent to a laboratory where the PSA concentration is measured using immunoassay techniques. Results are typically reported in nanograms per milliliter (ng/mL) and are usually available within 1-4 days. Your healthcare provider will contact you to discuss the results and their implications.

How Are PSA Results Interpreted?

PSA results are interpreted based on age-specific thresholds. Generally, PSA below 4.0 ng/mL is considered normal, but age-adjusted ranges provide better accuracy. A PSA below 1.0 ng/mL indicates very low risk of serious prostate cancer. Results above your age-appropriate threshold require additional evaluation.

Interpreting PSA results requires understanding that "normal" PSA levels vary with age. As men age, the prostate naturally enlarges, producing more PSA. Therefore, age-specific thresholds provide more accurate risk assessment than a single cutoff value.

Age-Specific PSA Reference Ranges

Special Considerations for PSA Interpretation

Several factors may modify how your PSA results are interpreted:

• 5-alpha reductase inhibitors: Medications like finasteride or dutasteride (used for BPH or hair loss) reduce PSA levels by approximately 50%. If you take these medications, your threshold should be halved accordingly.
• Hereditary risk: Men with family history of prostate cancer have a lower threshold of 2.0 ng/mL, regardless of age.
• Previous elevated PSA: If you've had prior elevated PSA investigations, individualized thresholds based on your history may apply.
• PSA velocity: An increase of more than 0.5 ng/mL per year may indicate concern even if the absolute value remains below threshold.

What Does an Elevated PSA Mean?

Elevated PSA does not automatically mean you have prostate cancer. The most common cause of high PSA is benign prostatic hyperplasia (enlarged prostate), which affects most men as they age. Other causes include urinary tract infections, prostatitis, and recent prostate manipulation. Only about 25% of men with elevated PSA who undergo biopsy have cancer.

When PSA levels exceed the threshold for your age, it indicates increased PSA production by the prostate. While this naturally raises concern about cancer, it's essential to understand that most elevated PSA results are not caused by cancer.

Common Causes of Elevated PSA

Benign Prostatic Hyperplasia (BPH): This is by far the most common cause of elevated PSA in men over 50. BPH involves non-cancerous enlargement of the prostate gland, which produces more PSA as it grows. Nearly all men develop some degree of BPH as they age, with prevalence exceeding 50% by age 60 and 90% by age 85.

Prostatitis: Inflammation of the prostate gland, whether bacterial or non-bacterial, can significantly elevate PSA levels. Acute bacterial prostatitis may cause dramatic PSA increases that normalize after treatment. Chronic prostatitis may cause persistent mild elevations.

Urinary Tract Infection: Infections involving the urinary tract or prostate can temporarily increase PSA levels. Testing should be delayed until several weeks after successful treatment to obtain accurate results.

Prostate Cancer: While concerning, cancer accounts for only a minority of elevated PSA cases. The probability of cancer increases with higher PSA levels, but additional testing is always needed to confirm or exclude the diagnosis.

Next Steps After Elevated PSA

If your PSA exceeds the appropriate threshold, your doctor will typically recommend further evaluation through a standardized diagnostic pathway:

1. Repeat PSA test: Sometimes recommended to confirm the elevation, especially if borderline
2. Digital rectal examination (DRE): Physical examination to detect prostate abnormalities
3. Free PSA ratio: Helps distinguish between cancer and benign conditions
4. Multiparametric MRI: Imaging that can detect suspicious areas within the prostate
5. Prostate biopsy: Tissue sampling for definitive diagnosis if indicated

What Does a Low PSA Mean?

A low PSA level is generally reassuring and indicates low risk of aggressive prostate cancer. Men with PSA below 1.0 ng/mL have very low probability of developing serious prostate cancer in the following years. For men over 65 with PSA below 1.0 ng/mL and no symptoms, additional routine PSA testing may not be necessary.

While much attention focuses on elevated PSA, understanding what low PSA means is equally important for making informed screening decisions. A PSA level below your age-appropriate threshold indicates the prostate is functioning normally and not showing signs of significant disease.

Research from large population studies demonstrates that PSA level has strong predictive value for future prostate cancer risk. Men with PSA below 1.0 ng/mL have approximately 0.5% risk of being diagnosed with prostate cancer within 6 years. This low risk profile allows for extended intervals between screening tests.

Testing Frequency Based on PSA Level

What Are the Benefits and Risks of PSA Screening?

PSA screening can detect aggressive prostate cancers early when treatment is most effective, reducing prostate cancer mortality by approximately 20%. However, screening also leads to overdiagnosis of slow-growing cancers that may never cause harm, resulting in unnecessary treatment with potential side effects including erectile dysfunction and urinary incontinence.

The decision to undergo PSA screening should involve careful consideration of both benefits and potential harms. This is why medical guidelines emphasize shared decision-making between patients and healthcare providers.

Benefits of PSA Screening

The primary benefit of PSA screening is the early detection of aggressive prostate cancers that might otherwise go undetected until they've spread beyond the prostate. When caught early, prostate cancer is highly treatable, with 5-year survival rates exceeding 99% for localized disease.

The ERSPC study, which followed over 180,000 men for up to 16 years, demonstrated that PSA screening reduces prostate cancer mortality by approximately 20% in men aged 55-69. For every 570 men invited for screening, one prostate cancer death was prevented over 16 years of follow-up.

Additionally, PSA testing can provide peace of mind for men with low levels, allowing them to reduce screening frequency and anxiety about prostate cancer risk.

Risks and Limitations of PSA Screening

The main concern with PSA screening is overdiagnosis—detecting cancers that would never have caused symptoms or death during a man's lifetime. Studies estimate that 20-50% of screen-detected prostate cancers fall into this category.

Overdiagnosis often leads to overtreatment, exposing men to the side effects of cancer therapy without corresponding benefit. Common side effects of prostate cancer treatment include:

• Erectile dysfunction: Affects 25-80% of men following treatment, depending on treatment type and baseline function
• Urinary incontinence: Ranges from occasional leakage to complete loss of bladder control
• Bowel problems: Particularly with radiation therapy
• Psychological impact: Anxiety and reduced quality of life from cancer diagnosis, even without treatment

The diagnostic pathway following elevated PSA also carries risks, including bleeding and infection from prostate biopsy, and anxiety during the evaluation period.

What If Cancer Is Found?

If prostate cancer is detected, treatment options depend on the cancer's grade and stage. Many low-risk prostate cancers can be safely monitored with active surveillance, avoiding immediate treatment and its side effects. Higher-risk cancers may require surgery, radiation, hormone therapy, or a combination of approaches.

A prostate cancer diagnosis does not necessarily mean immediate treatment is required. Modern approaches to prostate cancer management are highly individualized based on cancer characteristics and patient factors.

Active Surveillance

For many men with low-grade, localized prostate cancer, active surveillance has become the preferred management approach. This strategy involves regular monitoring through PSA tests, periodic biopsies, and sometimes MRI scans, with treatment initiated only if the cancer shows signs of progression.

Active surveillance avoids the side effects of treatment while maintaining the option for curative treatment if needed. Studies show that appropriately selected men on active surveillance have excellent long-term outcomes, with 10-year cancer-specific survival exceeding 98%.

Treatment Options

When treatment is indicated, options include:

• Radical prostatectomy: Surgical removal of the prostate gland
• Radiation therapy: External beam radiation or brachytherapy (radioactive seed implants)
• Hormone therapy: Medications that reduce testosterone levels
• Focal therapies: Treatments targeting specific tumor areas
• Combination approaches: Multiple treatments used together for advanced disease

The choice of treatment depends on cancer stage and grade, patient age and health, urinary and sexual function priorities, and personal preferences. Multidisciplinary consultation with urologists, radiation oncologists, and medical oncologists helps ensure optimal treatment selection.

Frequently Asked Questions