1
Q
What is mass screening?
A
Whole population (or subset of population)
2
Q
What is multiple or multiphasic screening?
A
Many screening tests at the same time
3
Q
What is targeted screening?
A
Groups with particular exposure
4
Q
What is case finding/opportunistic screening?
A
Tested while at doctors for another purpose
5
Q
What is the purpose of screening?
A
Early detection
6
Q
When is it ideal to screen?
A
- Inbetween the early diagnosis stage and usual clinical diagnosis stage (critical point 2)
7
Q
What are cases of disease determined by?
A
- Whether symptoms, signs, history and test results are normal (disease absent) or abnormal (disease present)
8
Q
What is the normal (common) disease given by? (%)
A
95% normal and 5% abnormal
- Normal distribution 2.5% + 2SD cut off
9
Q
What results in some healthy people on the abnormal side and vice versa?
A
- Distribution of measurements being used for both HEALTHY and DISEASED people
- tries to define cut off between the two groups
10
Q
To meet the requirements of screening, the disease will be…
A
- Common (prevalent)
- Severe consequences
- Early treatment has better outcomes than no treatment
- Considered a problem by people
- Natural history well understood
- Long preclinical ohase (so disease can be detected by the screening)
11
Q
To meet the requirements of screening, the test conducted will be…
A
- Having good accuracy OR high sensitivity and/or specificity
- Be safe
- Simple/ logistically manageable
- relatively cheap
- Acceptable to healthy people
12
Q
What is an example of diagnostic vs. screening for a woman with breast cancer?
A
DIAGNOSTIC: The woman found breast lump and goes to doctor the doctors conduct tests to investigate the lump
SCREENING: -Woman with no symptoms has regular screening mammogram
13
Q
What are some examples of diagnostic tests?
A
- Colonoscopy
- MRI
- Lumbar puncture
- Digital Rectal Exam
- Biopsy
14
Q
What are some examples of screening tests?
A
- FOBT (Faecal Occult Blood Test)
- PSA test (prostate)
- Pap smear
15
Q
Which parts of the table to sensitivity and specificity look at?
A
The columns
16
Q
Which parts of the table do PPV and NPV look at?
A
- Rows
17
Q
What is sensitivity ?
A
The probability of a positive test in people who have the disease (a/total diseased)
18
Q
What is specificity?
A
The probability of a negative test in people without the disease (d/nondiseased)
19
Q
What is specificity checking? (true negative, false negative etc.)
A
- Checking the true negative people (who have tested negative and are actually negative )
20
Q
What is sensitivity checking? (true,negative, false negative etc.)
A
- Checking the true positive (people who have the disease and have tested positive)
21
Q
What is Positive Predictive Value?
A
The probability that a person has the disease when the test is positive
22
Q
What is negative predictive value?
A
The probability that the person doesn’t have the disease when the test is negative
23
Q
What do you want to be high to avoid a false negative?
A
The NPV
24
Q
What is validity?
A
- Identifies as many people with the disease and ALSO without it
25
What does a sensitivity result of 44% mean?
- 44% of people with the disease will be correctly identified as having the disease
- Low value like this suggests test is not good at identifying people WITH the disease
26
What does a specificity result of 96% indicate?
- 96% were correctly identified as NOT having the disease
| - The other 4% got a false positive result
27
Which setting is the PPV of a test higher in (usually) ?
- HIGH prevalence setting
28
Which setting is the NPV of a test usually higher in?
- LOW prevalence setting
29
What is length time bias?
- Screening diagnoses diseases that are less aggressive than those that present clinically
- So you may present with tumors that are non agressive
- Treatments must be safe and effective
30
What is lead time bias?
- 'lead time' is EXTRA TIME you know that you have the disease from screening and makes it appear as if you live longer even if screening doesn't affect the survival case .
- So survival time shouldn't be used to evaluate screening test
31
What are interval cancers?
- Very agressive and presents usually BETWEEN screenings
32
What is an extension of length time bias?
- Overdiagnosis
| - Would never have detected the disease if you hadn't screened them.
33
What are NCDs (Non Communicable Diseases) also known as?
- Chronic diseases (e.g. cardiovascular disease)
34
Are NCDs more prevalent in low, middle or high income countries?
More prevalent in Low and Middle income countries
35
What was the role of the Ottawa framework?
- To provide new public health promotion strategies in industrialised parts of the world
36
Is health promotion just about being sick?
NO! It is also about being well
37
What is an example of equity and equality?
- Two people the same age and gender BUT one breaks their leg due to them living in housing that is of poor condition (unfair and unequal health status)
38
What is A determinate of health?
- Either factor OR characteristic that brings about change in heath either for BETTER or for WORSE
39
What are the 3 sections of health determinates?
1. Biological
2. Behavioural
3. Social ( environmental, cultural, economic)
40
What are social determinates of health?
- Circumstances where people are born, grow up, live, work and age & systems are put into place to deal with illness
41
What are social circumstances shaped by?
- Economics, social policies and politics
42
What are the 3 levels that interventions can be targeted at?
DOWNSTREAM
MIDSTREAM
UPSTREAM
43
What are examples of downstream factors and what level are they?
- biological factors at micro level
| - E.g. treatment systems, disease management, investment in clinical research
44
What are examples of midstream factors and what level are they?
- behavioural factors at intermediate level
| - E.g. lifestyle, behavioural and individual prevention
45
What are examples of upstream factors and what level are they?
- Social factors at the macro level
| - E.g government policies, population health, healthy environments
46
What are socio-ecological approaches from an upstream perspective?
1. Infrastructure and systems change (e..g policy and legislation such as seatbelts)
2. Community and health development (Engagement, community action)
47
What are lifestyle/behavioural changes approaches from a midstream perspective?
3. Health education and empowerment (knowledge, understanding and personal skill development)
48
What are primary care approaches from a down stream perspective?
4. Communication strategies (health info, behaviour change campaigns)
5. (Most Downstream) Disease Prevention e.g. primary,secondary and tertiary
49
What is primary disease prevention and what are some examples?
- Healthy promotion, focus on DISEASE FREE PEOPLE
| - e.g. vaccines, no smoking signs, encouraging activity, TAC safety adds, education on healthy eating
50
What is secondary disease prevention and what are some examples?
- At RISK populations- early diagnosis or shortening duration of disease
- e.g. get blood test for STI and get medication to get rid of the disease, screening for breast cancer, Exercise, Prostate test, Blood pressure
51
What is tertiary disease prevention?
- Treatment and management of people WITH DISEASE e.g. rehabilitation, group therapy, physio, diabetes management
52
What is the 'hug' prevention type?
- e.g. If you join health insurance you get free gym membership
- Or child gets $2 for every time they lose 300g (benefits-incentives)
53
What is the 'nudge' prevention type?
- Passive- for not doing much BUT you get a reward, e..g go in between the lines of the road)
54
What is the 'smack' prevention type?
- Actively do something and get a punishment e.g. parking in wrong spot and getting a ticket.
55
What is the 'shove' prevention type?
- You don't do anything wrong but get a punishment e.g. speed bumps put on the road to make you go slower -punishment is you must go slower)
56
What is community and health development about?
- Working WITH communities, not for them
57
What are challenges to health promotion?
- That people think we are a 'nany state' telling people what to do.
- Vested interests (e.g. lobbying and industry pressure)
- Evidence of effectiveness
58
What is a cluster?
- A group/aggregation of cases
59
What is an endemic?
- Permanent/regular disease incidence (normal level of disease) (cholera)
60
What is an outbreak?
- Same as an epidemic (may be smaller number of cases, area or population)
61
What is a pandemic?
- World-wide epidemic
62
What is an example of an endemic?
- Trochoma is endemic in the indigenous population (always occurring in the indigenous population due to no access of healthcare)
63
Why do outbreaks occur? (3 points)
1. Bringing disease into susceptible population
2. Bringing people into a place with where a disease readily exists (arrival of susceptible people into environment with endemic pathogen)
3. If something changes with the way a disease can spread ( effective route of transmission from source to susceptibles) e.g. Mosquito carrying disease with climate change creates new risk for disease.
64
Why would an outbreak investigation be done?
- To IDENTIFY the pathogen or source
- To CONTROL (STOP new cases)
- To PREVENT future outbreaks
(ICP)
- Also to learn more about a disease
- Training opportunity
65
What is the decision whether or not to do an outbreak invesitgation based on?
- Case numbers
- Disease Severity
- Risk to others
- Public/political/legal concerns
66
What are the 10 steps to an outbreak investigation?
1. PREPARE fore field work
2. VERIFY the existence of an outbreak
3. CONFIRM the diagnosis
4. DEFINE and identify cases
5. DESCRIBE/ORIENT data (Person, Place, Time)
6. DEVELOP hypotheses
7. EVALUATE hypotheses
8. REFINE hypotheses/perform additional studies
9. IMPLEMENT control and prevention measures
10. COMMUNICATE findings
67
What actions are involved in step 1 of an outbreak (PREPARE for field work)?
- EPIDEMIOLOGICAL HOMEWORK (what are the usual risk factors? Previous outbreaks?)
- SUPPLIES AND EQUIPMENT(competent lav, portable computer, phone, supplies)
- TEAM COMPOSITION (Who should be in the team? Statistical advisors, public relations, local info)
- ADMINISTRATIVE (Transport, communication. travel, cash, card, immmunisation, prophylaxis)
- PERSONAL
68
What actions occur in step 2 of outbreak investigation? (VERIFY existence of outbreak)
- So to make sure there are 'more cases than usual':
What is usual?
- Must have access to baseline data
- Specific to region
- Specific to current time
Where are the cases?
- Surveillance (monitoring of disease in populations)
- Different types of surveillance: passive, active, or sentinel (targeted)
Sources of info:
- Surveillance records
- Local/state health departments
- Other registries (hospital discharge records, death records, cancer or birth defect registries)
- Clinicians, labs, schools etc.
69
Where can there be false alarms in thinking there is an outbreak?
- Change in surveillance/policy of reporting
- Change in case definition
- Improved diagnosis (new test, more GP awareness et)
- Increased reporting
- Increased public awareness
- False positives in diagnostic tests
70
What action is taken in step 3 of an outbreak investigation? (CONFIRM the diagnosis)
Review the clinical findings (Death rate very high for cholera? What else could it be?)
- Review lab results of cases
-Be as specific as possible about causative agent (virus or bacteria)
- Talk to cases
Turned out to be Ebola !!
71
What action is taken in step 4 of an outbreak investigation? (DEFINE and IDENTIFY cases)
CASE FINDING OCCURS: Use lots of sources, labs and health care facilities, alert public and ask cases to identify themselves
Case definition is important and can change
- Sensitive vs. specific (captures all of the cases or a specific test which is laboratory findings)
- Patient diagnosis form
- Components include ; clinical features (bloody diarrhoea, gastroenteritis)
- Person- who do you want to include/exclude?
- Place (residence when they were infected. e.g. dined in restaurant)
- Time period of interest
- Lab results
- Divide the info into: CONFIRMED (Lab confirmed), PROBABLE (Lab results not available), and POSSIBLE (often less stringent clinical data)
72
What is a SUSPECTED case of Ebola?
- Any person, alive or dead with sudden onset of fever and having has contact with an Ebola case (suspected , probable or confirmed) or a dead or sick animal
73
What is an example of a PROBABLE case?
- Suspected case evaluated by clinician OR deceased suspected case with epi link to confirmed case
74
What is an example of a CONFIRMED case?
- Suspected or probable case with LAB CONFIRMATION
75
What is an example of a NON-CASE?
- Suspected or probable case with negative lab result
76
What challenges.barriers can occur in Step 4 of outbreak investigation when trying to detect a case?
- Lack of public understanding
- Lack of communication with public (on existence of outbreak, on role of imported healthcare workers)
- Community distrust
- Lack of inclusive planning for outbreak resolution
77
What action occurs in step 5 (DESCRIBE AND ORIENT DATA)?
For TIME: Draw an epidemic curve (e.g point source outbreak--> number of cases on y-axis, Time on x axis)
- Provides hints about source of outbreak
For PLACE: Map the data
For PERSON: Explore the data according to personal characteristics
78
What does a characteristic epidemic curve from point source outbreak look like?
- Steep upslope and a more gradual downslope
79
What does a curve look like that is an continuous extended source outbreak?
```
- Sharp swing up followed by a plateu (no increase or decrease ------) that corresponds to duration of exposure and then a right tail (down)
________
I \
I \
_ ____
```
80
What does a curve look like that is propagated or progressive outbreak?
- Series of progressively taller peaks one incubation period apart
- Disease is transmitted from person-person leading to serial transmission
81
What action occurs in steps 6-8 of an outbreak invesitgation?
- Develop/test/refine hypotheses
| - e.g. what is the source of infection, Case control or cohort study? , Other investigations?
82
What actions occur in step 9 of an outbreak investigation (IMPLEMENT CONTROL and prevention measures)
- Once source of outbreak has been identified, aim to break links in chain of infection and do it ASAP
e. g. remove contaminated food, steralise contaminated water, spray mosquitos/destroy breeding sites , prophylactic medication, behaviour midificaiton (convincing people to get treatment and alter burial ceremonies to prevent transmission of disease)
83
What are some barriers to care and outbreak control (step 9) in outbreak investigations in West Africa?
- Critically ill patients
- Remote, resource limited settings
- Poor understanding of infection control
- De-prioritisaton of patient care
- Reluctance of individuals to present of communities to identify ill person
- Affects outbreak control
- Resolve these issues and manage the outbreak
84
What were the priorities for Ebola outbreak responses?
- Identifying and treating all causes
- Gaining community trust
- Tracking every contact from every case
- Countering stigmatization and community mistrust
85
What actions occur in step 10 of an outbreak investigation? (communication of findings)
- Effective public relations strategy at the time of an outbreak is really important
- (front page headlines for days)
- May need them to spread info
- Also social media
86
What is a point source epidemic?
- Susceptible individuals exposed to simultaneously one source of infection
87
What is a propagated epidemic?
Where the disease is communicable- passed from person to person
88
What is an epidemic disease?
- Outbreak in particular region
89
What is a pandemic disease?
- Across international borders e.g. Cholera
90
What is the chain of infection pathway?
Infectious agent--> Reservoir--> Portal of exit--> Mode of transmission--> Portal of entry--> susceptible host (mist break mode of transmission to control disease properly)
91
What is virulence?
- Ability to cause disease (microorganisms pathogenicity)
- High virulence can cause diseases of greater severity but those with lower virulence can infect greater proportion of people
92
What are examples of indirect modes of transmission of a disease?
- Vehicle-borne,vector borne or air borne
- Vehicle= contaminated food, clothes, bedding, cooking utensils
- Vector= Agent carried by insect or animal
93
What does active surveillance involve?
- Collection of data from healthcare providers or institutions both as need arises and in the longer term
- Early warning systems (rapid response)
- Planned (chronic diseases, longer lag time)
- Notifiable diseases such as polio, hepatitis, TB
94
What is the difference between vaccination and immunisation?
Vaccination: PHYSICAL INJECTION of inactivated or weakened pathogen
Immunisation: Process that occurs AFTER vaccination (antibodies being produced)
95
How is influenza spread?
- Airborne droplets and incubation period 1-4 days
96
What is antigenic DRIFT?
- Minor antigenic changes caused by mutations
97
What is antigenic SHIFT?
- MAJOR antigenic changes resulting from genetic REASSORTMENT (involving recombination events between human and animal influenza viruses)
98
What is likely to be associated with Swine flu? (Antigenic DRIFT or SHIFT)
Antigenic SHIFT
99
• The pathogenicity of an agent refers to it’s ability to cause
disease (TRUE or FALSE)
TRUE
100
• If a pathogen has low virulence it is a severe disease (TRUE or FALSE)
FALSE (low virulence=low severity)
101
• The source of infection can also be a reservoir (TRUE or FALSE)
TRUE
| But reservoirs are not always the source of infection
102
• Communicable diseases are also known as contagious diseases (T/F)
FALSE!! Not all communicable diseases are contagious (human spread).
E.g. Malaria (vector spread) is communicable but NOT CONTAGIOUS
103
• Malaria is an epidemic in low-income tropical countries (T/F)
FALSE !
| Malaria is an ENDEMIC (normal) in low-income tropical countries. Relatively stable within the area.
104
• The cholera epidemic in the 1800’s was an example of a propagated epidemic (T/F)
FALSE! Cholera was a point source epidemic with the point being the water source (broadstreet pump)
105
If environmental conditions change then endemic disease may become epidemic (T/F)
TRUE! Natural disasters can lead to outbreaks for a number of reasons: poor access to clean, safe water (water-borne disease), overcrowding, injuries/wounds
106
The level of vaccination needed to achieve herd immunity varies by disease (T/F)
TRUE
| - Herd immunity thresholds vary between conditions. Measles is 90-95% where less contagious polio s 80-85%
107
Mycobacterium tuberrculosis is an example of an opportunistic pathogen (T/F)
TRUE
| Opportunistic pathogen requires depressed immune response
108
• Antigenic shift is a small change in the genes of the influenza
virus that happens continually over time. (T/F)
FALSE!
Antigenic shift is an abrupt, major change in the influenza A viruses, resulting in new hemagglutinin and/or new hemagglutinin and neuraminidase proteins in influenza viruses that infect humans
109
What is passive surveillance?
- Collection of data by health facilities as part of routine work of diagnosis and treatment. Data obtained only from people who seek help from health services (Health workers don't make effort to contact people)
e. g notifiable diseases being reported
110
What is active surveillance?
- Health professionals actively seek to collect data from all possible cases in their area. e.g. Immunisation
111
What is sentinel surveillance?
Monitoring of rate of occurrence of specific conditions to assess the stability or change in health levels of a population. It is also the study of disease rates in a specific cohort such as in a geographic area or population subgroup to estimate trends in a larger population.
112
What do sentinel health information systems do?
- Identifies if prevention or therapy isn't working as planned `
113
Would you have to do a case control or cohort for Ebola?
-No
114
What are case control/cohort studies good for?
- Infectious diseases such as food spread diseases in a buffet
115
Do we typically start with a case control in outbreaks?
YES! BUT if we can get the entire population or if we have a really good idea of the exposure then we do a COHORT study.
BMS1042
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