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Prostate-specific antigen wikipedia, lookup

Should I have that blood test for Prostate
PSA screening
• Understand what the PSA test is
• Identify when it should be used
• Describe the pros and cons of PSA testing
Prostate Cancer
• Commonest cause of cancer in men in the UK
• 2nd commonest cause of cancer death in men in the
• Average age of diagnosis is 70 – 74 yrs of age
• Much less common under 50 yrs of age
• Average age of mortality is 80 – 84 yrs of age
• 1 in 26 men in the UK will die from Prostate
Risk Factors for Prostate Cancer
• Age (strongest risk factor)
• Family history – especially if relative
diagnosed before age of 55 yrs
– Also link to BRCA 1 and 2 so consider FHx
breast cancer relative
• Black men > 3 times more likely than white
men (oriental/asian men lowest risk)
• Diet inconclusive
What is the PSA?
A Glyccoprotein which liquefies semen and aids sperm motility
PSA Testing
• ANY man aged over 50 who requests a PSA after careful
consideration should be tested
• Expressed in benign and malignant conditions
• Test benefits
– Diagnose cancer before symptoms
– Diagnose at a stage where could be cured or life extended
– Serial measurements may help in diagnosis
• Test limitations
– PSA not diagnostic or tumour specific
– False reassurance: 15% of men with a normal PSA will have
Prostate Cancer and 2-3% will have high grade Prostate Cancer
– Identification of cancers which may not become clinically evident
in the patient’s lifetime
• Sensitivity (rules diagnosis in)
– 21 % for all prostate cancers
– 51 % for high grade prostate cancers
– Using a PSA cut off of 4.0
• Specificity (rules diagnosis out)
– 91 % for all prostate cancers
– Using a PSA cut off of 4.0
• Positive Predictive Value (proportion of men with an
elevated PSA who have Prostate Cancer)
– 30 % for a PSA level of > 4.0
– Less than 1 in 3 men with a PSA of > 4.0 will have
Prostate Cancer detected on biopsy
Conditions for PSA testing
One should not check the PSA (has a half life of
2.2 days)
During an active UTI
If ejaculated within previous 48 hrs (rise of up to 0.8)
If exercised vigourously within previous 48 hrs
Had a DRE within 1 week (although some studies
suggest minimal rise 0.26 –0.4)
Had a Prostate Biopsy within 1 week (rise of 7.9)
Nb 5 Alpha Reductase inihibitors may reduce PSA by
50% within 6 months
DRE is useful for men with LUTS but not for
asymptommatic men
• If PSA raised above age specific limit
– Refer Urology 2WW