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Prostate-specific antigen (PSA) is a serine protease which is usually specifically expressed in the prostate. Measurement of serum PSA in serum is used widely for the diagnosis and monitoring of prostate cancer. Elevation of serum PSA is more a sensitive and specific indicator of prostatic carcinoma than prostatic acid phosphatase (PAP), being raised in over 90% of cases when carcinoma is first detected by comparison to 50% for PAP.
However, PSA lacks the required specificity to be a test for prostatic cancer
as it is also increased in most patients with benign prostatic hypertrophy.
There has been recent guidance as to the level of PSA test that indicates further
investigation is required (1). This reference range takes into account the patients
age.
| AGE (YEARS) |
PSA CUT OFF (ng/ml) |
| 50-59 |
>=3.0 |
| 60-69 |
>=4.0 |
| 70 and over |
>5.0 |
PSA is also used as a means of monitoring disease:
- if PSA > 40, there is a high chance that there is nodal or metastatic
spread
- if PSA > 100, there is almost certainly metastatic spread
Reference:
- NHS Cancer screening programmes - Prostate Cancer Risk Management Programme
(2002).
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