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Health and society > Block 10 > Flashcards

Block 10 Flashcards

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1
Q

Name some types of tests =

A

Biological - Hb, Ca2+, ALT
Images - CXR, mammogram, ultrasound
Questions - CAGE
Examination - tactile vocal fremitus

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2
Q

Tests act to

A

Shift our understanding on the continuum

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3
Q

A good test maximises what and minimises what

A 
Maximises = true positive and true negatives
Minimises = false positives and false negatives
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4
Q

True positive rate is the same as

A

Sensitivity

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5
Q

True negative rate is the same as

A

Specificity

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6
Q

Sensitivity definition =

A

Number of people with a positive test who actually have disease

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7
Q

Specificity definition =

A

Number of people with negative test who truly don’t hace disease

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8
Q

Sensitivity equation =

A

No of people with true +ve/all with disease

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9
Q

Specificity equation =

A

No of people with true -ve/all people without the disease

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10
Q

How can you summarise the impact of a test result?

A

PPV and NPV

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11
Q

PPV definition =

A

The change of really having disease with a positive test result

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12
Q

NPV definition =

A

The chance of really not having disease with a negative test result

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13
Q

PPV equation =

A

No. of true positives/all those who tested +ve

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14
Q

NPV equation =

A

No of true -ves/all those who tested -ve

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15
Q

Unlike NPV and PPV, sensitivity and specificity remain

A

Constant

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16
Q

What can change NPV and PPV?

A

Prevalence

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17
Q

What changes the prevalence?

A

Primary vs secondary care
Age
Country

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18
Q

Why are tests used differently in primary and secondary care?

A

DIfference in PPV and NPV

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19
Q

When prevalence increases …

A

PPV increases

NPV decreases

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20
Q

When prevalence decreases

A

PPV decreases

NPV increases

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21
Q

What can tell you how tests are best used in clinical practice?

A

Likiehood ratio

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22
Q

Each test has how many likelihood ratios?

A

2 - LR+, LR-

23
Q

LR+ =

A

Sensitivity/false +ve rate

24
Q

LR - =

A

Specificity/ false -ve rate

25
Q

Chances of disease after test =

A

Chances of disease before test x LR

26
Q

Screening =

A

Systematic appilation of a test to identify individuals at sufficient risk to warrent further investigation/prevention amongst persons who haven’t sought medical attention on account of symptoms.

27
Q

Examples of screening

A 
AAA
Diabetic eye
Blood spot
Newborn hearing
Newborn physical exam
Fetal anomalies
Breast, cervical, colorectal cancer
28
Q

Screening is what type of prevention?

A

Secondary

29
Q

When do we screen?

A
  • More definitive tests are risky or unpleasant
  • Limited opportunity for primary prevention
  • Treatment limited
  • Early treatment associated with better outcomes
30
Q

Screening occurs in what phase of a disease?

A

Presymptomatic phase

31
Q

Criteria to decide what is screened for can be broken into what categories?

A
  1. Disease
  2. Test
  3. Treatment
  4. Program
32
Q

Screening: the condition must be

A
  • Identifiable risk factor
  • Latent period
  • An important problem
  • Epidemiology and natural Hx well understood
  • All cost-effective primary prevention is exhausted
33
Q

Screening: the test must be

A
  • Simple, safe, precise
  • Acceptable
  • Have an identifiable cut off
  • Agreed management following positive result
34
Q

Screening: the treatment must be

A
  • Evidence that early treatment causes better outcomes
  • Agreed policies on who gets offered
  • Optimised before screening
35
Q

Screening: the program must be

A
  • Acceptable
  • Benefits>risk
  • Cost effective
  • Opportunity cost
  • RCT evidence it reduces mortality and morbidity
36
Q

Opportunity cost =

A

The loss of other alternative when one alternative is chosen

37
Q

What needs to be done before a screening test is rolled out?

A

Clinical trial

38
Q

Selection bias in screening RCTs

A

Healthy people tend to uptake screening

Length bias

39
Q

What is length bias?

A

Screening tends to pick up slower progressing diseases and these diseases automatically have better prognosis

40
Q

How do we get around selection and length time bias

A

Intention to treat/intention to screen analysis

41
Q

What is the lead time?

A

Time between detection of a disease and clinically apparent symptoms

42
Q

What is lead time bias?

A

Those with disease picked up through screening have a longer lead time so have a longer survival from diagnosis

43
Q

How do we get around lead time bias?

A

Measuring deaths prevented rather than survival

44
Q

Test for colorectal cancer =

A

Faecal occult blood

Flexi-sig

45
Q

Test for prostate cancer =

A

Prostate specific antigen (PSA)

46
Q

PPV of FOB

A

2%

47
Q

PPV for PSA

A

30%

48
Q

Who benefits from screening

A
  • Not false -ve
  • Not false +ve
  • True -ve somewhat
  • Some true +ves but not all
49
Q

What is the problem with prostate cancer screening?

A

Catch too many slow growers or non-progressors.

50
Q

What logic is at the heart of ethics?

A

Utilitarian

51
Q

Autonomy issues with screening:

A

Are people actually chosing, especially children and infants

52
Q

What is good about good screening?

A

Early detection can reduce risk of death or illness

53
Q

What is bad about good screening?

A

False +ves
Over investigation and treatment
Some people get true +ves but this doesn’t prevent deaths

Health and society (6 decks)

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