Limitations of prostate specific antigen (PSA) tests
If a man requests prostate cancer testing after being fully counselled on the benefits and risks, perform both prostate-specific antigen (PSA) test and digital rectal examination (DRE).
The PSA test measures PSA protein in the blood but there are many questions about the value of this test for prostate cancer as there are numerous limitations.
Poor sensitivity and specificity of the PSA testMost men who have a positive PSA result do not have prostate cancer.1
The PSA test is relatively insensitive; thus, a low PSA result (negative test) does not always correctly exclude the presence of prostate cancer.1
At a PSA threshold of 4.0 ng/mL there is:
- 20% sensitivity (i.e. proportion of positives who have the disease)
- 94% specificity is (i.e. proportion of negatives who did not have the disease)
- 37% positive predictive value (i.e. the proportion of positive test results in men with the disease)
- 91% negative predictive value (i.e. the proportion of negative test results in men without the disease).
High false-positive rate
In a large European trial of prostate cancer testing in men aged 50–74 years, 16% of all PSA tests were declared positive, but three out of four men (aged 55–69) with positive PSA tests did not have prostate cancer following biopsy.2
Reference ranges are not established
Normal values of PSA may be different for every man.
PSA values are adjusted upward with advancing age and the normalised values need to be considered:3
- 2.5 ng/mL for men aged 40–49 years
- 3.5 ng/mL for men aged 50–59 years
- 4.5 ng/mL for men aged 60–69 years
- 6.5 ng/mL for men aged 70–79 years
PSA levels can be raised in a range of conditions, other than prostate cancer
Raised PSA levels can occur with many other conditions, including benign prostatic hyperplasia (BPH), prostatitis, prostatic infarction, after an “aggressive” DRE, after bicycle riding or after ejaculation.1
Benign enlargement remains the commonest cause overall for raised PSA levels.
For more information
- Croswell JM, Kramer BS, Crawford ED. Screening for prostate cancer with PSA testing: current status and future directions. Oncology (Williston Park) 2011;25:452–60, 63. [PubMed]
- Schroder FH, Hugosson J, Roobol MJ, et al. Prostate-cancer mortality at 11 years of follow-up. N Engl J Med 2012;366:981–90. [PubMed]
- Oesterling JE, Jacobsen SJ, Chute CG, et al. Serum prostate-specific antigen in a community-based population of healthy men. Establishment of age-specific reference ranges. JAMA 1993;270:860–4. [PubMed]