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Flashcards in HaDSoc Week 6 Deck (36)
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1
Q

Define diagnosis

A

The definitive identification of a suspected disease or defect by application of tests, examinations or other procedures (which can be extensive) to definitely label people as either having a disease or not having a disease

2
Q

Give three methods for detection of disease

A

Spontaneous presentation
Opportunistic case finding
Screening

3
Q

What is spontaneous presentation?

A

Person presents with symptoms - self-defined as ‘patient’
To GP, A+E, other services
Diagnosis made

4
Q

What is opportunistic case finding?

A

Person presents with symptoms related to particular disease/problem
Health professional takes the opportunity to check for other potential conditions:
BP, urine dipstick

5
Q

Describe the process of diagnosis

A
Presentation
History, examinations, investigations
Either has the disease or doesnt
Treatment follows
Patient willing to accept reasonable risk of side effects in order to get well
6
Q

Define screening

A

A systematic attempt to detect an unrecognised/asymptomatic condition by the application of tests, examinations, or other procedures, which can be applied rapidly (and cheaply) to distinguish between apparently well persons of an identified high risk population, who probably have a disease (or its precursor) and those who probably do not. The screening provider then offers information, further tests and treatment. This is to reduce associated risks or complications.

7
Q

Describe the process of screening

A

Rapid/cheap test used on an appropriate population to identify high risk and low risk individuals for a particular condition.
Those that are identified as being high risk are then offered diagnostic tests which either show presence of disease or no disease.
The individuals identified as having the disease are then offered further information and treatment

8
Q

What is the purpose of screening?

A

Give a better outcome compared with finding something in the usual way (having symptoms and self-reporting to health services)
In other words, if the outcome of screening is the same as when treatment is given at the time of symptom presentation, then there is no point in screening
Finding something earlier not the primary objective

9
Q

Give some example of population screening programmes that run in the UK

A

Abdominal aortic aneurysm
Bowel cancer screening
Breast screening programme
Cervical screening programme
Diabetic eye screening programme
Foetal anomaly screening programme
Infectious disease in pregnancy screening programme
Newborn and infant physical examination screening programme
Newborn blood spot screening programme
Newborn hearing screening programme
Sickle cell and thalassaemia screening programme

10
Q

Give some examples of conditions which there are no screening programmes and why this might be controversial

A
Prostate cancer (PSA)
Breast cancer screening <50 years of age (except those in pilot study)
Cervical cancer <25 years of age

Public pressure - if someone is affected by a condition they may have trouble understanding why we dont screen for it - can only see it from their perspective

11
Q

What are the UK National screening committee criteria for deciding if there should be a screening programme for a condition/disease?

A
Condition
Test 
Intervention
Screening programme
Implementation
12
Q

What is meant by the national screening committee criterion, ‘condition’ ?

A

The condition has to be important in terms of frequency, severity - with epidemiology, incidence, prevalence and natural history being understood - have to know the difference that screening would make
All the cost-effective primary prevention interventions should have been implemented as far as practicable
If the carriers of a mutation are identified as a result of screening the natural history of people with this status should be understood, including the psychological implications

13
Q

What is meant by the national screening committee criterion, ‘test’?

A

Has to be simple and safe as they are asymptomatic - cant expose to unacceptable risks
Has to be a precise and validated screening test - need to trust the data it is giving you
Distribution of test values in the population must be known and an
agreed cut-off level must be defined and agreed - when should and shouldnt intervene
Acceptable to target population - e.g. Is the test invasive - what are the benefits v.s. The risks
Agreed policy on further diagnostic investigation of those who test
positive and choices available to them
If the test is for a particular mutation or set of genetic variants the
method for their selection and the means through which these will be
kept under review in the programme should be clearly set out

14
Q

What are the consequences of false positives?

A

Put the individual through stress, anxiety, inconvenience
Turned into patients when not actually ill
Invasive diagnostic tests - risks
Direct costs - staff, services
Opportunity costs - money that could be spent somewhere else
Lower uptake of screening in future –> greater risk of interval cancer
Low PPV –> lots of false positives

15
Q

What are the consequences of false negatives?

A

Inappropriate reassurance
Possibly delay presentation with symptoms - because they’ve been told they are fine so will dismiss the condition as an option
Not offered diagnostic test when may have benefited from it

16
Q

What are the features of test validity?

A

Sensitivity
Specificity
Positive predictive value
Negative predictive value

17
Q

What is sensitivity defined as?

A

The proportion of people who have the disease who will be correctly identified as having the disease (receive a positive result)
Also known as detection rate

18
Q

How is sensitivity calculated ?

A

People with the disease who tested positive (true positives) / total number of people with the disease (true positives + false negatives)

19
Q

What does sensitivity mean?

A

If the sensitivity is high then the test is very good at correctly identifying people with the disease you are screening for
A high sensitivity is ideal (although not always possible)

20
Q

What is specificity ?

A

The proportion of people who do not have the disease who are correctly identified as not having the disease (test negative)

21
Q

How is specificity calculated?

A

Number of people without the disease who were correctly identified as not having the disease (true negatives)/ Total number of people without the disease (true negatives + false positives)

22
Q

What does specificity mean?

A

If the specificity is high then the test is very good at correctly identifying people without the disease as not having the disease
A high specificity is ideal (although not always possible)

23
Q

What are the features of sensitivity and specificty?

A

Sensitivity and specificity are a function of the characteristics of the test
When the same test is applied in the same way in different populations the test will have the same sensitivity and specificity

24
Q

What is the positive predictive value?

A

The probability that someone who was identified as having the disease/tested positive for the disease actually has the disease
This is strongly influenced by the prevalence of the disease

25
Q

How is the positive predictive value calculated?

A

The number of people identified as having the disease (tested positive) who actually have the disease (true positives) / The total number of people who were identified as having the disease (tested positive) (true positives + false positives)

26
Q

What is the reason for considering carefully what population to screen ?

A

The prevalence of the condition affects the PPV
If the prevalence is high then the PPV will be high
If the prevalence is low than the PPV will be low e.g. More false positives will occur

27
Q

What is the negative predictive value?

A

The proportion of people identified as not having the disease (tested negative) who actually do not have the disease

28
Q

How is the negative predictive value calculated?

A

Number of people identified as not having the disease (tested negative) who actually do not have the disease (true negatives)/ The total number of people who were identified as not having the disease (true negatives + false negatives)

29
Q

What is the meaning of the national screening committee criterion, ‘intervention’?

A

Have to have an effective intervention for those identified through screening - have to have evidence that it improves outcome compared with people who present at symptomatic phase (usual care)
There should be agreed evidence based policies covering which individuals should be offered interventions and the appropriate intervention to be offered.

30
Q

What is meant by the national screening committee criterion, ‘screening programme’?

A

Proven effectiveness in reducing mortality or morbidity (high quality RCT data)
Evidence that the complete screening programme is clinically, socially and ethically acceptable to health professionals and public
Benefit gained by individuals should outweigh any harms for example from overdiagnosis, overtreatment, false positives, false reassurance, uncertain findings and complications
Opportunity cost of the screening programme should be economically balanced in relation to expenditure on medical care as a whole

31
Q

What is meant by the national screening committee criterion, ‘implementation’?

A

Clinical management and patient outcomes should be optimised in all healthcare providers
All other options for managing the condition should have been considered
Management and monitoring programme – quality assurance (e.g. Accuracy of results, how long it takes to get results etc.)
Adequate staffing and facilities for programme
Evidence-based information available to potential participants (informed choice)
Public pressure should be anticipated - decisions should be scientifically justifiable to the public

32
Q

What are some questions and debates concerning screening?

A

Is the natural history always understood?
How many abnormalities would regress spontaneously or never be problematic? E.g. Older men dying with prostate cancer rather than of prostate cancer
Are the ‘right’ people being screened? E.g. Hypochondriacs likely to attend lots of screening, have healthy behaviours etc. Also need to make sure screening a population where the PPV/ prevalence is as high as possible
Has screening caused any observed reduction in mortality?
Over-diagnosis and over-treatment?
Psychological impact?

33
Q

Why should screening programmes be evaluated?

A

Must be based on good quality evidence
Pressure from public e.g. Prostate cancer - but no robust evidence that earlier detection improves outcome - screening can cause harm - unnecessary treatment, can cause unwanted side effects

34
Q

Describe some evaluation difficulties

A

Lead bias - early diagnosis falsely appears to prolong survival
Only appear to survive longer because diagnosed earlier
Patients live the same length of time, but longer knowing that they have the disease

Length time bias - Screening programmes better at picking up slow growing, unthreatening cases than aggressive, fast-growing ones Diseases that are detectable through screening are more likely to have a favourable prognosis, and may indeed never have caused a problem Could lead to false conclusion that screening is beneficial in lengthening the lives of those found positive – curing people that didn’t need curing?

Selection bias - skewed by health volunteer effect
Those who have regular screening likely to also do other things that protect them from disease
An RCT would help deal with this - but difficult to carry out, especially for preexisting screening programmes

35
Q

What are some sociological critiques of screening programmes?

A

Victim blaming / Individualising pathology - a lot of responsibility on individuals to take part in screening - is everyone equally able
Individuals and populations increasingly subject to surveillance – prevention as social control?
Moral obligation - Difficult to decline screening - normative expectations about what is sensible and reasonable - if decide dont want to go for screening lots of reports as them being told they are being reckless, stupid etc. - financial incentive for encouraging people to take part in screening
Feminist critiques - Breast cancer screen and cervical cancer screens perpetuating the idea that women’s bodies are in some way less well designed/need more help???

36
Q

Why is there increasing emphasis on promoting informed choice and why is this sometimes difficult to achieve?

A

An essential attribute for any individual health professional…is to have a thorough grasp of the current state of the evidence for that particular intervention. They must clearly convey what is and what is not known, what is certain and the degree of uncertainty, so that people can make an individualised trade-off of potential benefits and harms in order to determine their own level of risk
Communicating benefits, harms and risks of preventative interventions can be challenging - lay person, public opinion, depends how much you know/up to date with research, depends how much is known by the scientific community in general