Prostate Specific Antigen
|
Assay |
Prostate Specific Antigen |
|
Key Words |
PSA |
|
Specimen Collection |
Serum (brown), Plasma (orange) |
|
Turnaround Time |
72hrs |
|
Test Indications |
Prostate specific antigen (PSA) is used as a tumour marker for prostate cancer. It can be used in diagnosis, where the higher the PSA concentration, the greater the probability of prostate cancer. Around 15% of men with PSA <4ug/L will have prostate cancer on biopsy, as will 25% of men with PSA 4-10ug/L and 50% of men with PSA >10ug/L. Confirmed levels of >100ug/L are consistent with metastatic disease. |
|
Limitations/Interferences |
No significant interferences from lipaemia, icterus, common drugs, rheumatoid factor etc.It is known that in rare cases PSA isoforms do exist which may be measured differently by different PSA tests. PSA is not known to be elevated in cancers of other origins, but a number of medical investigations or interventions (e.g. catherisation, cystoscopy, digital rectal examination, prostatic needle biopsy, prostatic massage, prostate ultrasonography, transurethral prostatic biopsy) can cause elevated concentrations, and 5-a-reductase inhibitors can decrease concentrations. Benign conditions that may cause elevated concentrations include acute urinary retention, benign prostatic hyperplasia, prostatitis and urinary tract infections. |
|
Reference Range |
0–39 yrs use clinical judgement 40-49 yrs </= 2.5 μg/L 50–59 yrs </= 3.5 μg/L 60–69 yrs </= 4.5 μg/L 70–79 yrs </= 6.5 μg/L 80+ yrs </= 7.5 μg/L*
* Referral criteria - PSA more than 20 or more than 7.5 and there are symptoms suggestive of metastatic disease (bone pain and/or fatigue and/or significant unintended weight loss)
The updated ranges are based on those in the NICE CKS on Prostate Cancer and are also in line with regional referral criteria for suspected prostate cancer. |
|
Analytical Error [1] |
3.5% |
|
21.1% |
