What Does a PSA Result Mean?

What prostate-specific antigen measures, why no PSA level proves or rules out cancer, what free PSA adds, what raises it temporarily, and what the US Preventive Services Task Force says about screening.

By [Author name]November 4, 20263 min read

Labs

A PSA result is a probability, not a diagnosis. Prostate-specific antigen is made by normal prostate cells as well as cancerous ones, so an enlarged or inflamed prostate raises it too. A level above 4.0 ng/mL is generally considered abnormal, but there is no level that means cancer, and no level that rules it out; the higher it is, the likelier cancer becomes. A high result is usually repeated before anything else, and the share of PSA that is free can help decide whether a biopsy is needed.

This article is general information, not medical advice.

What Raises PSA

The US National Cancer Institute (NCI) lists, besides prostate cancer:

Benign prostatic hyperplasia (BPH), the enlargement of the prostate common with age, and prostatitis, its infection or inflammation.
A recent biopsy, or an infection or inflammation, which can keep PSA raised for a month or two.
Ejaculation and vigorous exercise, such as cycling, which raise it briefly. The NCI notes that people are generally advised to avoid them for 2 days before a test.
Age: PSA rises with age, so some doctors use a higher cut-off, such as 5 ng/mL, for older men and a lower one, such as 2.5 ng/mL, for younger men.

Some medicines for BPH, finasteride and dutasteride, lower PSA, so a lower cut-off is used for men taking them.

Free PSA

Most PSA in the blood is bound to proteins; the rest is free. The free PSA percentage is free PSA divided by total PSA, and a lower percentage means a higher chance of cancer. In a 1998 study of 773 men with a PSA of 4 to 10 ng/mL and a normal prostate exam, Catalona and colleagues found that biopsying only men with 25% free PSA or less found 95% of cancers while avoiding 20% of unnecessary biopsies. It’s mainly used in that grey zone of total PSA.

Should You Be Screened?

The US Preventive Services Task Force (USPSTF) recommendation from 2018, which it is now updating, says:

Aged 55 to 69: the decision is an individual one, made after talking through the benefits and harms with a clinician. Screening may prevent about 1.3 deaths from prostate cancer over about 13 years for every 1,000 men screened, and about 3 cases of cancer that has spread. The harms include false-positive results, biopsies, and overdiagnosis: treating cancers that would never have caused symptoms, with risks such as incontinence and erectile dysfunction.
70 and older: it recommends against PSA-based screening, since the benefits don’t outweigh the harms.

The USPSTF notes that Black men and men with a family history of prostate cancer are at higher risk, which is worth raising with your doctor.

Reading Your Results Over Time

A single high result is often repeated; the NCI notes that a doctor may recommend another PSA test in 6 to 8 weeks to confirm it, then watch for a rise over time. After treatment for prostate cancer, the trend matters more than any one value. Comparing results means comparing like with like: the same kind of test, ideally from the same lab, without a recent ejaculation, ride, or infection.

Following It in Kaizora

Total Prostate-Specific Antigen, Free Prostate-Specific Antigen, and Free Prostate-Specific Antigen Percentage are lab results on Labs, each logged with its time, laboratory, and printed range, so a result outside the lab’s range is flagged. A result such as “< 0.1” after treatment is logged with its comparator, as the lab printed it. A draw’s results share their time and laboratory, so the total and free PSA from the same blood line up, and the chart shows the trend across years.

The Short Version

PSA comes from benign as well as cancerous prostate cells; no level proves or rules out cancer.
Above 4.0 ng/mL is generally abnormal; age, BPH, prostatitis, ejaculation, and cycling raise it.
A free PSA of 25% or less in the 4 to 10 ng/mL range makes cancer more likely.
The USPSTF leaves screening to an individual decision at 55 to 69 and recommends against it from 70.

Sources

National Cancer Institute, Prostate-Specific Antigen (PSA) Test.
US Preventive Services Task Force, “Screening for prostate cancer: US Preventive Services Task Force recommendation statement,” JAMA 319, no. 18 (2018): 1901–1913. doi:10.1001/jama.2018.3710; Prostate Cancer: Screening.
Catalona WJ et al., “Use of the percentage of free prostate-specific antigen to enhance differentiation of prostate cancer from benign prostatic disease: a prospective multicenter clinical trial,” JAMA 279, no. 19 (1998): 1542–1547. doi:10.1001/jama.279.19.1542

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