PSA - Worlds Favourite Tumour Marker Flashcards
Why do you measure serum tumour markers?
1) Detect malignancy and possibly identify the organ involved - screening/ diagnostic
2) establish tumour burden and predict response - prognosis/prediction
3) monitor in response to therapy and need for further therapy - follow up
What are general limitations of serum tumour markers?
1) lack of clinical specificity for cancer
- most markers are present in normal tissue
- many are elevated in benign disease
2) lack of clinical sensitivity for early cancers - only rarely elevated in early malignancy
3) rarely raised in all cancers of a particular type
- exception hCG
4) often raised in different cancers
Exception - PSA
What are some important consideration of tumour markers?
- Tumour markers should only be requested after considering the likelihood that the test result will improve patient outcome, increase quality of life, or reduce overall cost of care.
- inappropriately used tumour markers can cause patients additional anxiety and distress
- There is significant inappropriate requesting of tumour markers
What are the two prostatic diseases?
BPH - benign prostatic hyperplasia and prostate cancer
Symptoms of BPH?
Frequency, urgency, nocturia, dysuria, dribbling, incontinence, poor stream, hesitancy, retention, infection
Enlarged but smooth ad symmetrical gland on DRE
Symptoms of prostate cancer
Frequency, urgency, nocturne, dysruia, retention, back pain, weight loss, anaemia, obstruction, altered bowel movement.
Modular and stony hard prostate
What is the ideal prostate bio marker?
- in screening of symptomatic men is would identify men with cancer or premalignant disease likely or progress to aggressive prostatic cancer.
- Diagnosis / case finding - In symptomatic men it Would differentiate prostatic cancer from benign prostatic hyperplasia (BPH) and Would differentiate aggressive from indolent diseases
- monitoring - in patients with prostate cancer it would realisable confirm stable disease or indicate disease progression requiring intervention.
What is PSA?
Prostate specific antigen
What does PSA do as a bio marker?
Dissolves seminal coagulum to increase sperm motility
Circulates in free and bound forms in serum
decrease in free PSA is malignant prostate disease
How do you use PSA?
Screening/early detection
- population screening isn’t recommended and so an informed decision has to be made on whether or not to test.
Diagnostic aid - prostatic biopsy required one definitive diagnosis. Risk stratification - assessing the need for biopsy
Monitoring - active surveillance - should remain stable, post total prostatectomy (get rid of prostate) (undetectable), radiotherapy/endocrine therapy - rate of fall relevant to therapy
Establish quality requirements - what are the preanalytic requirements?
• Appropriate reason for request / prior discussion.
• Awareness of specimen requirements – e.g. stability
Establish quality requirements - what are the analytical requirements?
Well-standardized methods - acceptable specificity,sensitivity, precision, bias, stability etc
Established quality requirements - what is the post analytical requirements?
Consensus about reference intervals/decision pointsand interpretation.
Excellent communication between lab & clinic.
What are some other conditions that can raise PSA?
Benign prostatic hyperplasia, urinary tract infection, prostatitis and after catheterisation
Is there a guideline for men wanting to take a PSA test if they are unsymptomatic?
Yes
What are the timing requirements for the specimen once taken?
- Not in men with a urinary tract infection
- Prior to digital rectal examination or 1 week after
- At least 48 hours after ejaculation
- At least 6 weeks after prostate massage
- before or 1 week after ultrasound
- Before or 1 week after rigid cytoscopy
What are the storage requirements for a specimen?
- Up to 7 days at 4 degrees for total PSA / up to 2 years at -70 degrees
- For <2 days at 4 degrees for freePSA / up to 2 years at -70 degrees
- early separation of specimens desirable for free PSA
- stable for 5 freeze thaw cycles
Does catherisation increase PSA?
Yes
Immunoassay - analytical quality requirements?
Immunoassay for PSA must be accurately calibrated in terms of the international standard for PSA and must be equimolar
Independent assessment of both calibrations and equimolarity should be carried annually for all PSA assay used in the UK and for new PSA assays as they become available.
What are the lab responsibility for a PSA specimen?
- Ensure that rigorous internal quality control and external quality assessment systems are in place for PSA especially around decision limits
- State the name of the method used on the laboratory report
- Provide fully cumulated results to enable interpretation of trends in PSA results
- Confirm increases in PSA results as appropriate
Internal quality control?
You need to run a known value sample along with your sample and compare - make sure your doing it right.
Post analytic - intelligent reporting?
This includes highlighting trends and changes, interventions, clinical details and interpretative pitfalls.
What would a raised PSA result lead to?
Increased PSA Doesn’t necessarily indicate there is prostatic disease but a normal result doesn’t mean there is no malignancy
