PROSTATE SPECIFIC ANTIGEN (PSA)
12/06/2003
Prostate Specific Antigen (PSA )
Free PSA and Complexed PSA
Cancer Prostate is the most commonly diagnosed malignancy in men beyond age 50.
In recent years there has been a consistent increase in the worldwide incidence of clinically significant Cancer Prostate hand in hand with a decrease in mortality from the disease
Urologists agree that earlier detection through yearly (PSA) screening of men age 45 and beyond combined with advances in surgical and treatment options have contributed, to this positive trend.
Value of PSA testing
1. Early detection
PSA testing allows detection of prostatic cancer an average of 5.5 years before clinical detection.
2. Definitive diagnosis
Transrectal ultrasonography guided biopsy (TRUS) performed on the basis of clinical signs and symptoms, (DRE) and (PSA) will lead to definitive diagnosis and staging of the disease.
- Most men have blood levels under 4 ng/ml in the circulation which increases naturally in parallel with age.
- PSA levels between 4 and 10 ng/ml (also defined as gray zone level ) are associated with a 25% chance of having cancer prostate, or nonmalignant prostate disease such as Benign Prostatic Hyperplasis (BPH) and acute prostatitis or genitourinary medical intervention.
- Levels exceeding 10 ng/ml indicate a probability of prostate cancer greater than 67%, a probability that increases further with increasing PSA blood level.
3. Predict prognosis prior to therapy.
4. Monitor and follow up success of therapy.
5. Predict whether cancer is still confined or not to the prostate.
Value of free PSA and complexed PSA testing
PSA is a glycoprotein produced by epithelial cells in the prostate and found in semen and blood. Despite the worldwide use of PSA the specificity of the test is relatively low.
Total PSA measures both free PSA (unbound) and complexed PSA (bound to alpha-1 antichymotrypsin).
Measuring free PSA is particularly useful in the 4-10 ng/ml PSA concentration range. Complexed PSA fraction demonstrates a marked increase in specificity at low PSA levels from 2-4 ng/ml resulting in more accurate prostate cancer detect
|
