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PH4702- Professional Pharmacist > Screening > Flashcards

Screening Flashcards

1
Q

Warning

A
  • Personal experience
    • People close to us who have/had diseases where the outcome may have been better with screening
    • Personal experience of screening
  • Cultural and political dimension
    • Not based solely on evidence
      • US: periodic (annual health check)
      • UK: Long periods without any contact with health services
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2
Q

Definition

A
  • The presumptive identification of unrecognised disease or defect by the application of tests, examinations, or other procedures which can be applied rapidly. Screening tests sort out apparently well persons who probably have a disease from those who probably do not. A screening test is not intended to be diagnostic. Persons with positive or suspicious findings must be referred to their physicians for diagnosis and necessary treatment’
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3
Q

What are screening programmes

A
  • Screening is never just a test
  • Screening programmes
    • Need a coordinated response to the results of a test
      • Diagnosis
      • Treatment
    • Cost-effective
    • Continuous
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4
Q

WHO (Wilson and Junger) criteria (1968)

A
  • The condition should be an important health problem
  • There should be a treatment for the condition
  • Facilities for diagnosis and treatment should be available
  • There should be a latent stage of the disease
  • There should be a test or examination for the condition
  • The test should be acceptable to the population
  • The natural history of the disease should be adequately understood
  • There should be an agreed policy on whom to treat
  • The total cost of finding a case should be economically balanced in relation to medical expenditure as a whole
  • Case-finding should be a continuous process, not just a once and for all project
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5
Q

Why do we screen

A
  • Primary purpose of screening is to reduce risk
    • Reduce the risk of developing a disease
    • Reduce the risk of disease progression
    • Reduce the risk of death
    • Reduce the risk of an unwanted outcome (e.g. antenatal screening)
  • Very occasionally, screen merely for information
    • E.g. Screening for Down’s Syndrome where a couple have decided that, no matter what the result is, they will carry on with the pregnancy
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6
Q

Considerations before introducing a screening programme

A
  • Perfect screening test
    • Always right
    • Non-invasive
    • Not unpleasant
    • The disease would have a cure that was always successful and with no side effects
  • Have to weigh benefits and risk
    • Risk of harm with all screening interventions
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7
Q

Considerations- an example

A
  • A disease affects 1% of the population (n= 1000)
    • It is fatal
    • There is no treatment
    • The test for this disease is 90% accurate
  • If you screened this population for the disease, how many people will test positive
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8
Q

Positive or Negative- true or false

A
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9
Q

Sensitivity

A
  • The proportion of sick people who are correctly identified as having the condition
  • Sensitivity = True positives / All persons in population with a disease
  • Usually expressed as a percentage
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10
Q

Specificity

A
  • The proportion of healthy people who are correctly identified as not having the condition
  • Specificity = True negatives/ All persons in the population without disease
  • Usually expressed as a percentage
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11
Q

Sensitivity and specificity- worked example

A
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12
Q

Screening for motor neurone disease (MND)

A
  • Imagine you are the secretary of state for health
  • You are approached by a team from a world-leading university who demonstrate to you that they have developed a 100% accurate test for MND
  • They recommend that the population of England should be screened for MND
  • What would your response be and why
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13
Q

Lead-time bias

A
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14
Q

Prostate cancer

A
  • Most common cancer in men in UK
    • 47,740 new cases per year (2014-16 average)
    • 84% survival rate at 10 years
  • Usually develops slowly and asymptomatically
    • First signs often when prostate has enlarged to such a degree that it affects urinary flow
  • Difficult to distinguish between malignant and benign enlargements of prostate (BPH)
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15
Q

Prostate-specific antigen (PSA) test

A
  • Developed by Richard Albin
  • Designed to see if men with prostate cancer were responding to treatment
  • However, also the case that the higher the PSA level, the more likely there is a cancer present
  • 1986 FDA approved PSA for use in patients suspected of having prostate cancer
  • Started to be used as a screening test in men who were well and had no symptoms
    • By mid-1990s, several million PSA tests were being performed each year
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16
Q

PSA test: Evidence

A
  • PLCO (Prostate, Lung, Colorectal and Ovarian) Cancer Screening Study
    • n= 80,000
      • Randomised to intervention (PSA testing over 6 years) or control (usual care)
    • the rate of death from prostate cancer was very low and did not differ significantly between the two study groups
17
Q

Why doesn’t the PSA test reduce mortality

A
  • The higher the PSA level, the more likely there is cancer present BUY
    • PSA can be raised in infection or benign prostatic enlargement
    • Some cancers will not lead to increased PSA levels
    • 2 out of 3 men with an increased PSA will not have cancer
18
Q

Why doesn’t the PSA test reduce mortality

A
  • Some cancers which lead to an increased PSA level will be very slow-growing and may never cause any problems
  • Very poor indicator of cancer for 2 primary reasons
    • 1) Lots of false positives
      • Patients endure unnecessary, invasive biopsies
    • 2) Where true positive identified
      • Many patients would never develop the deadly form of the disease
19
Q

Overtreatment as a result of PSA test

A
  • Treatment for prostate cancer is frequently radical
    • Radiotherapy
    • Surgery
    • Chemotherapy
  • Potential side effects of these interventions include
    • Pain
    • Incontinence
    • ED
  • Only 16% of US prostate cancer patients die from the disease
20
Q

PSA- a public health disaster

A
  • No difference in outcomes between radical prostatectomy, radiotherapy, active monitoring or watchful waiting
  • PSA test
    • PSA testing can’t detect prostate cancer and, more important, it can’t distinguish between the two types of prostate cancer- the one that will kill you and the one that won’t
21
Q

Breast cancer

A
  • 55,213 cases in the UK (360 in men)
  • Prognosis
    • Very much dependent on the type of cancer and how early the cancer is diagnosed
    • Significant improvements in survival rates over the last 20 years
      • May be due to screening but may also be due to better treatment or lifestyle changes
22
Q

Breast self-examination

A
  • Women in the UK instructed to be breast aware
    • Should know how their breast usually feel
    • Assumes women will spot changes and that the identification of any changes will lead to earlier identification of breast cancer
23
Q

Breast mammography

A
  • X-rays of each breast
  • NHS breast screening programme
  • Women aged 50-70 screened
    • Will be extended to cover women aged (47-73)
    • Attend for mammogram every 3 years
24
Q

Size of the tumour at the time of diagnosis before and after the introduction of mammography

A
25
Q

Breast mammography: risk v benefit

A
  • Welch and Passow
    • If 1000 women aged 50 years are screened annually for a decade
      • 0.3 to 3.2 will avoid a breast cancer death
      • 3-14 will be overdiagnosed and treated needlessly
      • 490-670 will have at least 1 false alarm
  • Gotzsche
    • If 1000 women invited for screening throughout 10 years
      • 0.5 will avoid dying of breast cancer
      • 5 healthy women will be treated unnecessarily
      • More than 100 women will experience important psychological distress including anxiety and uncertainty for years because of false-positive findings
26
Q

Lung cancer- targetting of low-dose CT screening

A
  • 26,604 participants
    • 55-74 years old
    • Minimum of 30 pack-years of smoking
    • Max 15 years since quitting
  • Divided into quintiles according to risk
    • Quintile 1 (lowest risk)- 0.15-0.55% risk of lung cancer
    • 2= 0.56-0.85%
    • 3= 0.85-1.23%
    • 4= 1.24-2%
    • 5= >2%
27
Q

Positive screening results

A
28
Q

The number needed to screen

A
29
Q

Lu-Ca deaths prevented by low dose CT

A
30
Q

Summary

A
  • Screening distinguishes apparently well persons who probably have a disease from those who probably do not. A screening test is not intended to be diagnostic
  • Decisions relating to screening are often not based on robust evidence
  • ALL screening tests have harms that need to be considered alongside any potential benefits
  • Pharmacies are already involved in screening and this involvement seems likely to increase in the future

PH4702- Professional Pharmacist (8 decks)

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