The “free” PSA test -- often written as PSA-f or FPSA, or referred to as a percent-free PSA -- can help many men avoid biopsies who have elevated PSA levels.
Because many factors other than cancer can elevate a regular PSA test result, the free PSA test gives additional information that can spare some men of unnecessary biopsies.
Conversely, the free PSA can act as a kind of safety net for patients who have a suspicious PSA level but their biopsies come back negative (no found cancer). If this is the case, a repeat biopsy is in order.
Free PSA: What It Means?
PSA floats in the blood in two forms – attached (or bound) to blood proteins and unattached ( or unbound) to blood proteins.
The free PSA test measures the proportion of unattached PSA to the total PSA in the blood sample.
The percentage of free PSA is lower in men who have prostate cancer than in men who do not.
According to American Cancer Society, men with free PSA at 7 percent or lower – meaning 7 percent is floating freely and unattached to blood proteins – prostate cancer is likely and the patient should undergo a biopsy.
Many doctors advise that men "consider " a biopsy if the level of free and unbounded PSA is between 7 percent and 25 percent, although the 25 percent threshold is not agreed upon by all doctors.
Other factors, such as the PSA velocity -- how quickly the PSA level has climbed -- may factor in to a physician's recommendation to get a biopsy.
A high free PSA -- above 25 percent -- usually indicates BPH (benign prostate hyperplasia) and not cancer.
Helps Avoid Unnecessary Biopsies
Using these cutoffs can help doctors detect prostate cancer with more certainty than a single, straight-foward PSA test.
Importantly, the free PSA test can help some men who have elevated PSA levels but also high free PSA results to avoid unnecessary prostate biopsies. At this point, the doctors may look for another condition, such as prostatitis, that may be causing the elevated PSA level.
When Is Free PSA Test Used?
The initial PSA test is generally not strong evidence of prostate cancer, so the follow-up free PSA test is usually performed if the original results are suspicious.
This test helps a physician decide if the patient should have a prostate biopsy, especially if the regular PSA results are in the borderline range -- between 4 and 10 ng/mL.
What If the Biopsy is Negative?
If biopsy comes back negative but free PSA remains low, a repeat biopsy is in order. That would suggest that the biopsy – which typically removes 12 small snips of prostate tissue – may have missed the cancer.
What is a Normal PSA Level?
A so-called ‘normal’ PSA level seems to be a bit of a moving target. Because of various factors such as age and medications, PSA levels tend to fluctuate. One abnormal PSA test can be quite meaningless.
That said, most doctors agree that a PSA level of 4.0 or below is considered to be safe and normal. Any consistent rating from 4.0 up to 10.0 is labeled suspicious and may require additional tests – such as a free PSA test. Above 10.0 ng/mL, more tests are definitely called for.
Other articles on prostate disease and prostate cancer.
