PSA, or prostate-specific antigen, is a protein made by prostate tissue. The blood test measures its concentration in serum, and it is ordered when prostate conditions are being assessed. It is not specific to prostate cancer, and a raised result has several explanations. The range printed on your report decides how the value is read.
The name is the source of most of the confusion. Prostate-specific antigen is specific to prostate tissue, not to cancer, and that distinction changes how a result is read.
What the test measures
PSA is a protein produced by the cells that line the prostate, a gland that sits below the bladder in men. Its usual role is to liquefy semen after ejaculation. Small amounts of PSA leak into the blood, and the blood test measures that concentration. Because the protein comes from prostate tissue in general, it is produced by an enlarged prostate and by inflamed or infected prostate tissue, as well as by prostate cancer.
A report may print total PSA, which is the main measurement, and some laboratories also print free PSA, the fraction that is not bound to protein. Free PSA is usually reported as a proportion of the total, and the proportion can be written as a ratio. A laboratory may also print a comment when a sample was collected soon after a procedure or when a medicine that lowers PSA is recorded.
Why it may be ordered
- When prostate-related symptoms are being assessed, alongside an examination and the rest of the picture.
- When a known prostate condition is being followed over time.
- Before or after a prostate procedure, where a clinician wants a baseline or a comparison.
- When prostate cancer screening is being discussed, a use that different guidelines approach differently.
- When a medicine that affects the prostate or lowers PSA is being taken, because the result is read with the medicine list.
- As part of a men's health package, where it is often grouped with other tests even though it is not a hormone.
The unit on your report
| What you may see | Unit | What it reflects |
|---|---|---|
| PSA, total PSA, prostate-specific antigen | ng/mL | The total PSA concentration in serum, in nanograms per millilitre. |
| PSA, total PSA | ug/L | The same concentration in micrograms per litre. For PSA the two units give the same number, because both are mass per volume. |
| Free PSA | percent of total PSA | The share of PSA that is not bound to protein, usually reported alongside the total. |
| Free to total PSA ratio | unitless | The same comparison written as a ratio rather than a percentage. |
Free PSA is not a second, independent measurement of cancer. It is a laboratory comparison that some clinicians use as context when the total is raised, and it is read with its own reference information.
Why this page does not print a range
PSA ranges differ by laboratory, assay, and calibration, and some laboratories print age-related ranges because PSA tends to rise with age and with prostate size. Sex is not a variable in the way it is for a hormone test, because PSA comes from prostate tissue. A man's result can also be compared with his own previous values rather than with a population range. Medicines used for prostate enlargement lower PSA, and a laboratory or clinician may account for that.
The range printed on the report that produced your value is the one that applies. Doctano keeps that printed range with the result and does not replace it with a general range. Where a report prints an age-related range, read the value against the one that matches the person's age.
What a high value can mean
A result above the report's range means the PSA concentration is higher than the laboratory's interval. Possible explanations include benign enlargement of the prostate, inflammation or infection of the prostate, a urinary infection, recent ejaculation, a recent prostate biopsy or catheter, and prostate cancer. Assay differences between laboratories can also move a result.
That list is the reason a raised PSA is not a cancer result. The test cannot tell which of those explanations applies, and it cannot distinguish a slow-growing prostate cancer from a more aggressive one on its own. A clinician reads the value with the examination, the trend over time, and other investigations. The result does not confirm or rule out cancer.
What a low value can mean
A result below the report's range means the PSA concentration is lower than the laboratory's interval. Low values are common, because PSA is produced by prostate tissue and the amount in blood is small. A low result is usually not interpreted on its own.
Two things complicate a low value. Some medicines used for prostate enlargement lower PSA, so the number may look lower than the prostate's activity would suggest. And a PSA inside the report's range does not rule out prostate cancer, because some prostate cancers do not raise PSA. After surgical removal of the prostate, PSA is expected to fall substantially, and a clinician reads any later change in that context.
What can move the value
- Recent ejaculation. It can raise PSA for a period, and a clinician may ask about the timing of the sample.
- Infection or inflammation. A urinary infection or prostate inflammation can raise the value.
- Prostate procedures. A biopsy, a catheter, or surgery can change PSA, and the report may note a recent procedure.
- Medicines. Some medicines used for prostate enlargement lower PSA, and a clinician can say whether a medicine is relevant.
- Age and prostate size. PSA tends to rise with age and with a larger prostate.
- Assay and calibration. Different laboratories and methods can produce different results on the same sample.
What to compare it with
Read PSA with the trend from the same laboratory, because a single value says less than a series. Where a report prints free PSA, read it with the total. A clinician may also use the prostate examination, a urine test for infection, and imaging, depending on the picture. Comparing a PSA result with a hormone result on the same report is not a like-for-like comparison, because PSA is not a hormone.
How to see the trend
Doctano reads the PSA value, its unit, and the reference range printed on the report. It keeps the range with the result, normalizes the marker name across laboratories, and places the value on the profile's timeline. Each point still opens the report it came from, so a note about a recent procedure stays with the value it describes.
Because PSA assays differ, a change is easier to trust when both results came from the same laboratory and method. Verify the value and the unit against the original report before reading a change as real.
What this page is not
This page explains the test in general. It does not interpret your result, diagnose a condition, or recommend treatment. It is not medical advice. Verify the value and the unit against the original report, and discuss the result with a qualified professional.