Prostate-Specific Antigen (PSA) is a protein produced primarily by the cells of the prostate gland, located beneath the bladder in men. Small amounts naturally circulate in the bloodstream, and a blood test measures its concentration in nanograms per milliliter (ng/mL). The PSA test is a common screening tool used to monitor prostate health and can serve as an early indicator of potential issues. However, PSA is not a specific marker for malignancy; any disturbance to the prostate can cause its levels to rise. Because PSA values fluctuate, a single test result is rarely used to make a definitive diagnosis. Understanding the factors that influence these measurements is necessary for accurate interpretation.
Everyday Activities That Temporarily Alter PSA
Physical manipulation or high pressure on the prostate gland can cause a transient spike in the amount of PSA released into the bloodstream. Ejaculation is a well-documented cause of temporary PSA elevation. Experts often advise abstaining from sexual activity for at least 48 hours before a blood draw to avoid a misleading result, as the mechanical process forces PSA-rich fluid from the prostate.
Vigorous physical activity, particularly long-distance cycling, can also increase PSA levels due to the sustained pressure placed on the perineum and the prostate. Activities that involve irritation to the pelvic area should be avoided before the test. Even a digital rectal examination (DRE), where a physician palpates the prostate, can briefly raise the antigen level. Doctors often draw blood for the PSA test before performing a DRE to ensure the most accurate baseline reading.
Chronic Non-Cancer Conditions That Raise PSA
Chronic, non-malignant conditions can cause a sustained, long-term elevation in a man’s baseline PSA level. Benign Prostatic Hyperplasia (BPH), a non-cancerous enlargement of the prostate, is one of the most common causes of sustained elevation, affecting many men as they age. In BPH, the prostate gland’s overall volume increases, and since more tissue is present, more PSA is naturally produced and leaks into the blood. This increase is proportional to the gland’s size over time, leading to a gradually rising baseline.
Prostatitis, which is inflammation or infection of the prostate, is another frequent cause of elevated PSA, sometimes resulting in a more dramatic spike than BPH. The inflammatory process disrupts the barrier between the prostate cells and the surrounding blood vessels, allowing a greater quantity of PSA to leak rapidly into the circulation. Acute bacterial prostatitis can cause the highest PSA levels, but these usually return to normal once the infection is treated.
How Prostate Cancer Impacts PSA Readings
When prostate cancer is present, it can cause PSA levels to increase because malignant cells often produce a higher amount of the antigen per cell than normal prostate tissue. Rather than relying on a single high reading, physicians often evaluate a pattern of results over time, a measurement known as PSA velocity. A rapid or sustained rise in the PSA level can be an indicator of a more aggressive form of the disease. Interpreting this velocity is complex, as studies have shown conflicting evidence on its stand-alone value in early cancer detection.
To add context to an elevated total PSA, other measurements are often employed, such as the free-to-total PSA ratio and PSA density. The free PSA test measures the amount of unbound PSA compared to the total amount, with a lower ratio suggesting a higher probability of cancer. PSA density calculates the PSA level in relation to the prostate gland’s volume, which helps to account for the size-related elevation seen in BPH. These secondary metrics help to stratify the patient’s risk, guiding the decision on whether further invasive procedures, like a biopsy, are necessary.
Medications and Testing Variables Affecting Results
External factors, including specific medications, can significantly alter the measured PSA number regardless of the underlying health of the prostate. Medications called 5-alpha reductase inhibitors, such as finasteride and dutasteride, are prescribed to treat BPH and work by shrinking the prostate gland. These drugs can reduce the total PSA level by approximately 50% after several months of use. This lowering effect must be accounted for by doubling the measured value for accurate interpretation. Other common drugs, including statins and non-steroidal anti-inflammatory drugs (NSAIDs), may also cause a slight decrease in PSA due to their anti-inflammatory properties.
The testing process itself can introduce variability into the results. Differences in the laboratory equipment and the specific commercial assay used to measure the antigen can lead to slightly different readings from the same blood sample. Assays standardized to the World Health Organization (WHO) reference, for example, may yield results that are up to 23% lower than those using the Hybritech standard. This inter-assay variability means that consistent testing at the same laboratory is preferred for tracking a patient’s PSA trend over time.