PSA Test: Explained
PSA stands for
- P-rostate
- S-pecific
- A-ntigen
An antigen is just a protein so they would’ve made it easier if they had called it a PSP – prostate specific protein. Then at least it would mean something.
The only organ in a man’s body that can make PSA is the prostate. PSA produced in the prostate normally “leaks” into the bloodstream and causes no harm. As men grow older, the prostate always grows and this leads to more PSA leaking into the bloodstream. Therefore, it makes sense that a “normal” PSA for an older man should be higher than for a younger man. The reported laboratory cut off for an abnormal PSA is up to 4.0 but that designation does not account for the age of the man. The threshold for an abnormal PSA should be higher than 4.0 for an older man and lower for a younger man. The normal PSA for men in each decade is seen below.
Ages :
- 40-49 Normal PSA is 0-2.5
- 50-59 Normal PSA is 0-3.5
- 60-69 Normal PSA is 0-4.5
- Over 70 Normal PSA is 0-6.5
Not all physicians use this normal range for each age group but most Urologists do as there are many good studies that support it’s use.
The other method of assessing the true risk of a man’s chance of having prostate cancer is the measurement of total PSA and the Free to Total PSA ratio described elsewhere on the website.
PSA is a protein that is only produced in the prostate. PSA can float in the bloodstream by itself or “hooked on” to other proteins. We can measure the amount of PSA free-floating or hooked on to other proteins and make a ratio of these two numbers.
Free to total ratio normals are as follows:
- >25 normal and a lower chance of having prostate cancer
- 16-24 probably still normal.
- 10-15 start worrying about the presence of prostate cancer
- <10 worry a little more.
Elevations in the total PSA drive the decision to pursue a prostate biopsy more than the free to total ratio numbers described above. Various factors regarding family history of prostate cancer and age adjusted PSA’s play a big role in deciding who needs a prostate ultrasound and biopsy.