The PSA test: what it measures, what screening trials show and why one result is not a diagnosis

The PSA test is among the most familiar blood tests offered to older men, and its number is easy to misread. A report on TODAY on October 10 made one point about it: a single result, high or normal, settles very little.

That is a fair summary of a test with an unusual history. It can find prostate cancer years before symptoms. For a long time the trials could not agree on whether finding it early saved lives. Longer follow-up has now given a clearer answer, which is that screening prevents a small number of prostate cancer deaths and, along the way, finds many cancers that never needed finding. What happens after a raised result has also changed.

What the PSA test measures

The prostate is a small gland below the bladder that makes part of the fluid in semen. It also makes a protein called prostate-specific antigen. TODAY’s report describes the test as one which measures the amount of a protein called PSA found in the blood.

A cancer in the prostate tends to push the level up, which is why the test is used to look for the disease. And the disease is common. A 2025 review in JAMA, a leading medical journal, opens with the scale. Prostate cancer is the most common nonskin cancer in men in the US, with about 299,000 new cases and 35,250 deaths estimated for 2024.

Most prostate cancers are found early and grow slowly. At diagnosis, approximately 75% of patients have cancer localized to the prostate, which is associated with a 5-year survival rate of nearly 100%. Localized means it has not spread. An additional 10% of men have distant metastases that are associated with a 5-year survival rate of 37%. Metastases are tumors that have seeded elsewhere in the body.

The US Preventive Services Task Force (USPSTF), an independent panel that assesses screening, put the same contrast in lifetime terms. In the United States, the lifetime risk of being diagnosed with prostate cancer is approximately 13%, and the lifetime risk of dying of prostate cancer is 2.5%. The median age of death from prostate cancer is 80 years, the median being the middle value.

More than 50% of prostate cancer risk is attributable to genetic factors, the review says, and age and race matter too. It gives yearly rates of 173.0 cases per 100,000 Black men against 97.1 per 100,000 White men.

Why one PSA result is not a diagnosis

PSA is made by the prostate, not by cancer as such. Anything that disturbs the gland can raise it. Firas Abdollah, a urologist at Henry Ford Health, gave TODAY a list that included a prostate infection, a recent medical procedure or even riding a bike, along with some medicines.

The reverse also happens: some men with prostate cancer have a PSA in the normal range. For both reasons Abdollah’s message was that one test is not sufficient, whichever way it comes out.

There is no single line between normal and abnormal. Two of the trials described here acted on a level of 3. In a large UK trial, men received a single invitation for a PSA screening test with subsequent diagnostic tests if the PSA level was 3.0 ng/mL or higher. The units are nanograms per milliliter of blood.

A raised number starts a process. Traditionally the next step was a biopsy, in which a needle takes small samples of the prostate to be examined under a microscope. Often it is first a repeat test. Abdollah described how, for some patients, the plan is to schedule another PSA test, usually for the following year, and watch the trend.

The absence of symptoms tells a man little either way. The Task Force notes that many men with prostate cancer never experience symptoms and, without screening, would never know they have the disease. That is the opening for screening, and it is also where overdiagnosis comes from, as described below.

What screening trials show about PSA testing and deaths

The central question is whether men who are screened die less often of prostate cancer. The longest-running test of it began in 1993 across eight European countries. Its main analysis covers a predefined core age group of 162,236 men who were 55 to 69 years of age at the time of randomization. One group was invited for repeated PSA tests and the other was not.

The final report came in late 2025. After a median follow-up of 23 years, prostate cancer mortality was 13% lower in the screening group. In absolute terms, the absolute risk reduction was 0.22%. An absolute reduction is the plain difference in the share of men who died, here about 2 fewer in every 1,000.

The trial’s authors translated that into numbers of men. Over 23 years, one death from prostate cancer was prevented for every 456 men invited to screening. Set against diagnoses, the paper reports that one death from prostate cancer was averted for every 12 men in whom the cancer was found, a figure that on the trial’s other numbers corresponds to the extra cases screening turned up. At 16 years the figures had been 628 and 18. The benefit of screening arrives late, because the cancers it catches would have taken many years to kill.

A British trial tested something more modest, one invitation to one test. It included men aged 50 to 69 years identified at 573 primary care practices in England and Wales, more than 400,000 in all. At 15 years, 0.69% of the invited men had died of prostate cancer against 0.78% of the others. That is a real difference and a small one, about 1 fewer death per 1,000 men.

Pooling the trials has changed the verdict over time. In 2018, a meta-analysis for the BMJ, a British medical journal, concluded cautiously that at best screening for prostate cancer leads to a small reduction in disease-specific mortality over 10 years. It put the size at one less death from prostate cancer per 1000 men screened over 10 years.

A new pooling in May 2026 had the benefit of the longer follow-up. It combined five trials with 721,607 participants followed for 11 to 23 years, and rated the evidence that screening reduces prostate cancer deaths as high in certainty, in its words a finding that contrasts with earlier evidence syntheses. Its authors were careful about what follows from that. This finding does not in itself justify population-based screening or imply that every well-informed individual would elect to undergo screening.

One thing no analysis has shown is a difference in deaths overall. The 2018 review found that screening probably has no effect on all-cause mortality. In the British trial, 23.2% of invited men and 23.3% of the others had died of any cause at 15 years. Prostate cancer is a small share of all deaths in older men, so even a real effect on it is hard to see in the total.

The harms of PSA screening: overdiagnosis and treatment

Screening finds more cancer. In the European trial, the cumulative incidence of prostate cancer was higher in the screening group than in the control group, by 30%. Cumulative incidence is the share of men diagnosed over the whole period.

Some of those extra cancers were caught in time to matter. Many were not going to matter. Overdiagnosis means finding a cancer that would never have caused symptoms or death in the man’s lifetime. A Swedish research team states the problem flatly. Screening for prostate cancer is burdened by a high rate of overdiagnosis.

The British trial shows where the extra diagnoses fall. Its authors reported that the PSA screening intervention increased detection of low-grade and early-stage cancers, and did not increase detection of the aggressive or advanced ones.

An overdiagnosed cancer cannot be told apart from a dangerous one with certainty at the moment it is found, so many have been treated. Treatment has costs. The Task Force’s figures for surgery are stark. About 1 in 5 men who undergo radical prostatectomy develop long-term urinary incontinence, and 2 in 3 men will experience long-term erectile dysfunction. Radical prostatectomy is removal of the whole prostate.

There are costs before treatment as well. Potential harms of screening include frequent false-positive results and psychological harms, the Task Force says. A false positive is a raised result in a man who turns out not to have cancer. Biopsies carry a small risk of serious infection.

The Task Force’s own summary of the benefit side sits beside those harms. The panel estimated that screening programs in men aged 55 to 69 years may prevent approximately 1.3 deaths from prostate cancer over approximately 13 years per 1000 men screened. Screening programs may also prevent approximately 3 cases of metastatic prostate cancer per 1000 men screened.

What happens after a raised PSA test now

Two changes in practice have aimed at keeping the benefit and shedding some of the harm.

The first is the scan before the needle. Magnetic resonance imaging (MRI) can show which parts of the prostate look suspicious, so that a biopsy can be aimed at them, or skipped if nothing shows. A Swedish trial tested this in screening. The researchers invited 37,887 men who were 50 to 60 years of age to undergo regular prostate-specific antigen (PSA) screening, and about half took part. Participants with a PSA level of 3 ng per milliliter or higher underwent magnetic resonance imaging (MRI) of the prostate. One group then had biopsies only of areas the scan flagged. The other had those plus the traditional pattern of samples from across the gland.

Low-risk cancers of the kind that rarely cause harm were found in 0.6% of the scan-guided group and 1.2% of the other. The authors concluded that the approach reduced the risk of overdiagnosis by half at the cost of delaying detection of intermediate-risk tumors in a small proportion of patients.

The second change is that a diagnosis no longer means immediate treatment. For lower-risk cancers, doctors can watch closely and treat only if the cancer shows signs of growing. The JAMA review estimates that one-third of patients with localized prostate cancer are appropriate for active surveillance with serial PSA measurements, prostate biopsies, or magnetic resonance imaging. Serial means repeated over time.

The evidence that monitoring costs few lives comes from a British trial that grew out of PSA testing. Between 1999 and 2009 in the United Kingdom, 82,429 men between 50 and 69 years of age received a prostate-specific antigen (PSA) test. Of those found to have localized cancer, 1,643 agreed to be assigned at random to monitoring, surgery or radiotherapy.

After 15 years, very few had died of the disease, whatever they were assigned. Death from prostate cancer occurred in 45 men (2.7%): 17 (3.1%) in the active-monitoring group, 12 (2.2%) in the prostatectomy group, and 16 (2.9%) in the radiotherapy group. Monitoring was not free of consequences. Metastases developed in 51 men (9.4%) in the active-monitoring group, in 26 (4.7%) in the prostatectomy group, and in 27 (5.0%) in the radiotherapy group. But a quarter of the monitored men avoided treatment altogether. In the active-monitoring group, 133 men (24.4%) were alive without any prostate cancer treatment at the end of follow-up.

The European trial’s own balance improved for a different reason, longer follow-up. Its authors wrote that long-term follow-up confirms a sustained reduction in deaths from prostate cancer with PSA testing, alongside an improved harm-benefit ratio.

What US guidance says about PSA screening

The Task Force statement of 2018 remains the reference point in the United States. It does not tell men in the main age group to be screened or not to be. Its conclusion is that the net benefit of PSA-based screening for prostate cancer in men aged 55 to 69 years is small for some men, and that the balance depends on how each man weighs a small chance of avoiding a cancer death against a larger chance of side effects.

For older men it is more definite. The panel concluded that the potential benefits of PSA-based screening for prostate cancer in men 70 years and older do not outweigh the expected harms.

The JAMA review describes where professional bodies have settled since. Recent guidelines encourage shared decision-making for prostate-specific antigen (PSA) screening. Shared decision-making means the choice is made by doctor and patient together after the trade-offs have been laid out.

The Task Force statement predates the 23-year European results, the MRI trial and the 2026 pooling. Whether it would be worded the same way today is an open question.

What the PSA evidence cannot tell an individual

One man’s result. Trial figures are averages across hundreds of thousands of men. They cannot say whether a given man’s raised PSA reflects a dangerous cancer, a harmless one or no cancer.

Deaths overall. Screening lowers deaths from prostate cancer. No trial has shown that screened men live longer overall.

Men at higher risk. The big trials were run in Europe. Black men have higher rates of the disease, and men with a strong family history do too. The balance of benefit and harm may differ for them, and the trials were not built to measure it.

Today’s pathway. Most of the mortality evidence comes from men screened in the 1990s and 2000s, before MRI and before active surveillance became routine. The harms then were larger than they are likely to be now.

Whether PSA testing makes sense for a particular man, and what a given result means, is assessed by their doctor.

A PSA result is the start of an inquiry, and on the trial evidence that inquiry prevents a few prostate cancer deaths at the cost of many more diagnoses.