Public Health, Critical Appraisal, Epidemiology and Statistics Flashcards
The WHO made a list of 6 ‘building blocks’ required to build an adequate health system - what are they?
- Service Delivery
- Health Workforce
- Information about helath needs
- Financing
- Medical leadership
- Adequate technology, equipment, vaccinations etc.
The WHO has published a list of ‘Sustainability Development Goals’ (SDGs). How many goals are there?
17 goals with 169 sub-targets
What are the current LMIC availabilities for WASH facilities in health care settings?
38% have no good water source
35% have no good soap source
19% have poor sanitation
What are the WHO pillars of a health system?
- Equity –> giving according to need
- Efficiency –> giving the greatest benefit within the resources that are available
- Safety –> care and treatment is beneficial and safe
- Patient Centredness –> patients should be involved in decision making and their cultural beliefs/values/attitudes should be respected
- Timeliness –> good care is given without delays
- Effectiveness
What is the Donebedian Healthcare Quality of Care Structure?
System based on health system perspectives
- STRUCTURE: System characteristics, money and resoucrces, facilities available, HMIS
- PROCESS: Staff characteristics, ethical, socially acceptable, approrpriate and effective medical care
- OUTCOMES: Patient characteristics –> morbidity and mortality, patient satisfaction
What does the term ‘closed setting’ mean?
Closed setting: an area in which people are in a closed environment (e.g. refugee camp) living in extremely close proximity
high risk of rapid disease spread and epidemic
(in this vein, a slum might be a semi-closed setting, and a rural village may be considered an open setting)
What are the 4 most common causes of death in refugee camps?
Measles
Diarrhoea
Acute respiratory illness
Malaria
List some diseases in which WASH is useful to prevent spread in refugee camps/closed environmetns
Diarrhoea
Malaria
Guinea worm
Trachoma
Scabies
Yellow fever
Dengue
Schistosomiasis
Chagas
Typhus
Trypano
etc etc etc
What WASH techniques are aimed at reducing reservoirs?
Water supply improvements
Excreta disposal
- VIPs
Wastewater management
Waste management
Vector control
dead bodies management
Define Crude mortality rate
The crude death rate is calculated as the number of deaths in a given period divided by the population exposed to risk of death in that period.
In terms of WASH, what are examples of groundwater?
Hand dug wells (must be protected)
Protected springs
Tube wells / boreholes
What are the advantages and disadvantages of Surface Water use for WASH?
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Visible and accessible
Simple adduction
Available quantities are seen
- Poor microbiology qualtiy –> you need to treat it
Prone to artificial pollution
What are the advantages and disadvantages of Groundwater use for WASH?
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Generally good quality (micro-biologically)
Better protected against artificial pollution
- Access can be difficult and expensive
Variable quantities of available water with rainfail
Sometimes salty taste
Risk of toxic minerals
What are the advantages and disadvantages of Precipitations use for WASH?
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Quality is usually quite good in rural areas
Easy to collect
- Not available year long in many places
Large storage capacity might be needed
What are minimum water quantities for people in emergency situations? (i.e. imagine you have been asked to set up a camp for DPs)
Minimal for Survival: 3-5 liters
Standard: 15-20
Amount we use in the UK per person per day? >100
What are minimum water quantities for Health Structures in emergency situations? (i.e. imagine you have been asked to set up a camp for DPs)
Outpatient Department:
5L/p/day
Hospital:
40-60L/patient/day
Surgery:
100-200L /p/day
What are the characteristics of potable water?
- Contains no pathogens
- Has a low concentration of toxic substances
- Is clear (low turbidity)
- Is not salty
- Has no colour, odour nor taste
Can you consume water that has e. coli in it? is it ever acceptable?
*****This is not the reality in most humanitarian cases if you are using anything other than bore holes / quality groundwater
How can you do mass water filtration?
Coagulation/flocculation
Assisted sedimentation
Rapid sand filtration
Chlorination
How long should water be boiled for to eliminate pathogens?
1 min from when the water started boiling
(add 1 minute for every 1000m elevation gain)
What are some examples of defecation sites you could create (±in a humanitarian emergency)?
Defecation Fields
- very arid areas only
Trench Latrines
Family Trench Latrines
Improved trench latrines
- Strict minimum for a humanitarian response
Pit latrines
Children latrines
- Smaller excreta holes and foot holds are smaller
Pour-Flush Latrines
- Needs 1-4L of water to flush; do not use this system in an area where you already have limited H20 supply
- only use these ni acute emergenicies if there is a strict demand
Raised Pit latrine
- useful in areas with high water tables, areas of flooding
VIP Latrine
- not recommended in emergencies because complex to build
Septic Tanks
- not recommended in emergencies because complex to build
Plastic Bag Latrines
- need for biodegradable plastic bags
- need for daily follow up
- need for good hygiene promotion
Chemical toilets
Fix existing toilet facilities
What type of defecation site is the BARE MINIMUM of acceptability in a humanitarian crisis?
Improved Trench Latrines
- walls for privacy and concrete/plastic slab to stand on
What are requirements for safe menstrual hygeine toilet facilies?
- Safe and private place
- Able to change pads 3+ times daily
- safe to use at nighttime
- Discreet
Is it better to bury or cremate the body of a person infected with VHF?
Bury - virus does not live well underground
What is the minimum depth a person must be buried?
How far from the water table?
1m underground
1.5m above water table
What are the 4 main categories of medical waste?
Sharps
Softs
Organics
Hazardous
name the 500 medications on the WHO essential list of drugs
JUST KIDDING please do not take any time to learn this
Which SDG focuses on elimiation of NTDs?
3 - Health and Wellbeing for all
But really you could make any of them fit the bill:
e.g.
SGD 4 Education – NTDs impact on health of school children-attendance and education
performance; indirectly because children act as carers and parents cannot afford fees due
to NTDs
SDG 5 Achieve Gender equality -Disproportionate impact on girls and women- anaemia
(schisto and hookworm); urogenital schistosomiasis and HIV. Access to praziquantel
The SDG and Roadmap for elimination of NTDs focus on 4 targets to reach in NTD control by 2030. What are these 4 targets?
- 90% reduction in patients requiring treatment for NTDs
- 75% reduction in DALYs lost to NTDs
- 100 countries have eliminated at least one NTD
- Complete eradication of 2 NTDs
The Global Burden of Disease Study looked at NTDs and DALYs. How many DALYs did it estimate are lost annually to NTDS?
27 million DALYs
Which 5 Public Health strategies can be used to address/manage NTDs?
- Vector Control
- WASH
- Preventative chemotherapy
- Appropriate disease management
- Treatment of zoonotic reservoirs
What is the definitiion of a HEalth System?
All the organisations, institutions, resources and people whose primary purpose is to improve health
What s the ‘One Health’ Framework from the WHO?
Environmental Health
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Human Health
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Animal Health
What are the ‘Building Blocks’ of a WHO health System
Service Dlivery
Health Work Force
Health information systems
Medicines and Technologies
Financing
Leadership and Governance
What are the 6 WHO regions
1 African Region (AFR)
2 Region of the Americas (AMR)
3 South-East Asian Region (SEAR)
4 European Region (EUR)
5 Eastern Mediterranean Region (EMR)
6 Western Pacific Region (WPR)
In regards to analysing research, what is the ‘DAFI DUCK’ method?
D - Description
A - Appraisal of methods
F - Findings
I - Interpretation
What study design is considered the Gold Standard for appraising the effectiveness of an intervention?
Randomised Control Trial
In regards to RCTs, how can authors prevent Selection Bias?
Generation of a random sequence to determine participant outcome
Allocation Concealment (e.g. single blind vs double blind)
I regards to RCTs, how can authors prevent performance bias and detection bias?
Blinding
What is attrition bias?
outcome data are missing due to attrition (withdrawal from the study).
This can lead to the systematic differences between groups and biased effect estimates
What is selection bias?
when the intervention and control groups in an RCT are systematically different,
i.e. the people in the intervention group have more severe disease than the control group, or are older, or have a higher proportion of malnutrition.
These systematic differences would bias the
result
What is the aim of blinding in an RCT?
To prevent:
- performance bias
- selection bias
What are Performance and Detection Bias?
participants or researchers know which treatment group the participant has been allocated to.
This can influence how the participant experiences or reports symptoms or drug side effects, or influence how the researcher measures and records trial outcomes
How can you prevent skewed results from an Attrition Bias in an RCT?
An intention-to-treat (ITT) analysis
All patients are followed up re: outcomes/included in the trial regardless of whether their outcome
What is Reporting Bias?
With-holding facts that don’t fit the agenda of your research hypothesis (e.g. not commenting on statistically insignificant things can be just important)
Name three ways you could randomly allocate patients to avoid Selection Bias
- A random number table
- Using a computer random number generator
- Coin tossing
- Shuffling cards or envelopes
- Throwing dice
- Drawing of lots
What are two methods you can use to analyse a trial?
DAFI DUCK method
AMSTAR method
What is a systematic Review?
A review of the literature conducted using systematic and rigorous
methods to answer a specified question.
This includes an extensive
search, an assessment of the risk of bias of all the studies, and synthesis of the results across trials (sometimes using meta-analysis)
What is a Meta Analysis?
A method for combining the results of different trials statistically.
It is one element of a systematic review, and should never be done
outside of a systematic review.
(note: a systematic review and a meta-analysis are not the same thing - though they are often discussed as if they were)
In regards to study outcomes, What is a dichotomous outcome? How is it statistically expresed?
An outcome where there are only two possibilities (e.g. mortality vs survival at one year)
They are summarised as:
Risks
Rates
Odds
What is a continuous outcome?
An outcome which occurs on a scale, with lots of possible measures.
i.e. weight, or height, or time to recovery
Summarised as a mean, meadian or mode
What is Risk?
Outcome / Total Population
can be expressed as:
- a proportion (10 out of 100 people died),
- a decimal (0.1),
- a percentage (10%), or
- per unit population (100 per 1000 children)
(Because its literally just one of two outcomes)
What is Rate?
Risk + Time
e.g. 12/1000 children per year
What is the Odds?
Number of people WITH outcome / Number of people WITHOUT outcome
Should be described as a decimal or ratio
Should NOT be described as a percentage; percentage is the way we exclusively discuss risk
What is Risk Ratio (relative risk)
risk in the intervention group / risk in the control group
Table 1 in the AQUAMAT paper (above) describes the baseline characteristics of the group of children treated with quinine, and the group of children treated with artesunate.
These characteristics are either ‘dichotomous’ variables or ‘continuous’ variables.
A dichotomous variable only has two options (yes/no, alive/dead, present/absent) and can be summarized as a percentage (risk) or a ratio (odds).
A continuous variable has a whole range of possible outcomes on a scale (1kg, 2kg, 3kg, etc), and can be summarized as an average (such as mean or median) plus a measure of the spread of values (such as standard deviation or range)
Which of the outcomes below are dichotomous? (more than one option may be correct)
Question 1 options:
a. Age (years)
b. Blantyre coma score
c. Severe anaemia (haemoglobin < 50 g/L)
d. Weight (kg)
e. Convulsions on admission
C and E
Convulsions on admission and severe anaemia are dichotomous variables.
You should also note that ‘haemoglobin’ is actually a continuous variable. However, in this case it was dichotomised into severe anaemia (< 50 g/L) or no severe anaemia (>50 g/L).
Age, weight and Blantyre coma score are continuous variables. Age and coma score were summarized as median (interquartile range,) and weight was summarized as mean (standard deviation).
Table 1 was provided in the paper to demonstrate that the randomization process in the trial worked, and that the two groups were similar at the start of the trial.
Table 2 of the AQUAMAT paper (above) provides the outcome data of the trial. All the outcomes are dichotomous.
Dichotomous outcomes can be summarized as Risk or Odds.
Risk is calculated by dividing the number of people with the outcome by the total population. It can be expressed as a percentage or a decimal.
What is the risk of death in those treated with artesunate (Mortality; ITT analysis)? (more than one option may be correct)
Question 2 options:
a. 8.5%
b. 0.093
c. 0.109
d. 0.085
A, D
In table 2 (above), the authors have chosen to compare dichotomous outcomes using Odds Ratio (OR).
Odds Ratio is calculated as the odds of death in those treated with artesunate (0.0927) divided by the odds of death in those treated with quinine (0.1229) = 0.75
Most people find Risk Ratio (also known as Relative Risk) easier to understand than Odds Ratio. In this paper the authors could have used either.
The Risk Ratio is calculated by dividing the risk of death in those treated with artesunate by the risk of death in those treated with quinine.
What is the Risk Ratio for death when using artesunate compared to quinine?
a. 1.29
b. 0.75
c. 0.78
The Risk Ratio is calculated by dividing the risk of death with artesunate (0.085) by the risk of death with quinine (0.109) = 0.78.
Note that the effect size appears slightly bigger when using Odds Ratio compared to the Risk Ratio.
In regards to AQUAMAT
You have calculated that the risk ratio of treatment with artesunate vs. quinine is 0.78. What does a Risk Ratio of 0.78 mean? (more than one answer may be correct)
Question 4 options:
a. It means 78 less people will die if treated with artesunate instead of quinine
b. It means that if you treat people with artesunate their risk of dying is 22% lower than if you treat them with quinine.
c. It means that the risk of dying if treated with artesunate is 78% of the risk of dying if treated with quinine.
d. It means 78% of those treated with artesunate will die.
It is correct to say that ‘The risk of dying if treated with artesunate is 78% of the risk of dying if treated with quinine.’
However, the easiest and most common way to interpret a Risk Ratio is to say ‘if you treat people with artesunate their risk of dying is 22% lower than if you treat them with quinine’.
Technically this is known as the ‘Relative Risk Reduction’ and is calculated simply as 1-Risk Ratio.
A risk Ratio of 0.78 means that the risk of dying is 22% lower if treated with artesunate.
Do you think that this is a clinically important effect? Is it a big effect? Is it worth doing?
a. Yes
b. I don’t know
c. No
B. I dont know
It is actually impossible to know how big an effect is from the Risk Ratio alone. To understand the size of the effect we need to know how common death is if treated with quinine.
This is similar to when a shop window has a sign saying ‘20% off’. You won’t know how much money you will save until you know the price of the item you want.
When do you use GRADE?
Used to assess the quality of results of a systematic review
What tests can you do check heterogeneity of studies when looking at a Forest Plot
- The eyeball test – Do the 95% confidence intervals of all trials overlap (pictured)
- Chi2 p-value = The probability that the observed differences between trials occurred by chance
- I2 test = The percentage of observed variation between trials that is not due to chance
What is a Meta Analysis?
A way of combining results from a number of individual trials to produce a summary result
What is a Forest Plot?
A forest plot displays the summary result of a meta analysis and the results of the individual studies
What is GRADE?
Grading of Recommendations, Assessment, Development and Evaluation when assessing RCTs
An approach to formulating:
*Evidence-based recommendations
*transparent and systematic process
*explicit link between evidence and recommendations
How do you classify studies using GRADE?
High
Moderate
Low
Very Low
Using GRADE, What 5 things might cause you do downgrade an RCT from high quality evidence to moderate/low/very low?
*Risk of bias - is the risk of bias large enough to make you question the plausability of the outcomes?
*Inconsistency - Are the studies too heterogenous to compare?
*Indirectness - Are the studies actually addressing the question you are studying?
*Imprecision - would you overall outcome change if the upper and lower levels of the CI were true?
*Other (publication bias)
What is the Number Needed to Treat (NNT)?
The Number Needed to Treat (NNT) is the number of patients you need to treat to prevent one additional bad outcome (death, stroke, etc.).
e.g. if a drug has an NNT of 5, it means you have to treat 5 people with the drug to prevent one additional bad outcome
How do you calculate NNT?
NNT is the inverse of ARR
SO
First calculate the ARR:
ARR = CER (Control Event Rate) – EER (Experimental Event Rate)
Then calculate the inverse of ARR
SO
If we use the picture example:
0.096 - 0.028 = 0.068
1/0.068
14.7
NNT = 14.7 (round to 15 since you can have part of a person)
What 4 principles underline ‘Good Health’
- Biological
- Psychological
- Social
- Cultural
What are the 4 historical eras of public health?
- Sanitary awakening
- Personal Protection
- Therapeutic Era
- New Public health
What are the 10 Essential Public Health Operations according to the WHO?
EPHO 1 Surveillance of a population’s health and well-being
EPHO 2 Monitoring and response to health hazards and emergencies
EPHO 3 Health protection including environmental, occupational, food safety and others
EPHO 4 Health promotion, including action to address social determinants and health inequity
EPHO 5 Disease prevention, including early detection of diseases
EPHO 6 Assuring governance for health and well- being
EPHO 7 Assuring a sufficient and competent public health workforce
EPHO 8 Assuring sustainable organizational structures and financing
EPHO 9 Advocacy, communication and social mobilization for health
EPHO 10 Advancing public health research to inform policy and practice
***faculty of PH and CDC have created the same principles
What are the three domains of public health?
Health protection
Health improvement
Health services
Which is expressed as a rate - incidence or prevalence?
incidence
What is incidence?
Number of new cases of a disease occurring in a given population over a given amount of time
What is prevalence?
The total number of people living with a disease at a specific moment in time.
What is a standardised mortality rate?
statistically constructed summary rates that account for the differences
between populations with respect
to other variables, such as age, sex
and race.
An SMR of 100 means that people in the group are dying at the same rate as in the standard population
SMR > 100 means death rates are higher, usually reflects worse health than average
SMR < 100 means death rates are lower, usually means health is better than average in this area
E.g. SMR of 168 in area A means death rates in area A are 68% higher than in standard population
A population in Area A has an SMR 142 - what does this mean?
Deaths rates are 42% higher in Area A compared to the standard population
What are three examples of descriptive studies
Correlational (ecological) study
Case reports / case series
Cross sectional studies (surveys)
What are three examples of Analytical studies?
Cohort
Case control
Intervention e.g. RCT
What are Ecological Studies?
Ecological studies compare disease frequencies between different groups during the same period of time or in the same population at different points in time
Often provide clues about determinants of disease that
can be used for further research
Usually, cannot tell which came first, exposure or the disease, so good for finding out if there is an association
rather than cause and effect, e.g. individuals with cancer have a low serum beta – carotene. Is this a cause or an effect?
What are cohort studies?
▪ Cohort studies are a type of
observational study used to help find the association between cause and effect
▪ You observe what happens to groups of people over time and there is NO intervention
Name 2 advantages and 2 disadvantages of a cohort study?
ADVANTAGES
- Low risk of bias
- Good for looking at rare exposures
- can assess the effects of multiple exposures at the same time
- Can get a temporal (time
related) sequence between
exposure and outcome as all
individuals must be free of
disease at the beginning of the
study.
DISADVANTAGES
- can take a long time
- Loss to follow up (this can lead to attrition bias)
- expensive and resource intensive
- bad for looking at rare diseases
What is a case control study?
A group of people with a disease are compared to a group without the disease from the same population.
e.g. men in their 50s who have hypertension vs. men in their 50s who do not
Compare exposure to risk factors in both groups
Able to look at many different possible risk factors
Able to study diseases with a long latency period
Most common analytic study design seen in medical literature today
Particularly susceptible to bias
Comparatively less expensive
Give one advantage and one disadvantage of an RCT?
PROS:
- Gold standard
- provides powerful evidence on the effect an intervention has on an outcome
CONS:
- hard to get ethical approval
- expensive
- difficult to design and conduct
You want to explore new cases
of HIV in a community over one
year. The best measure is;
A. Prevalence
B. Incidence
C. Either incidence or
prevalence, doesn’t
matter which
B. Incidence
What is the leading cause of death globally?
IHD
What is the role of the WHO?
To give world-wide leadership and guidance in the field of health
To set global standards for health
To cooperate with governments in strengthening national health programmes
To develop and transfer appropriate health technology, information and standards
Monitor the health of countries
World Health Assembly (WHA) supreme decision making body with delegates from all 194 member
states
What are the 9 components of SDG, as it relates to health?
3.1 Reduce maternal deaths
3.2 End preventable deaths of new borns and under 5s
3.3 Communicable diseases –> end the epidemics of AIDS, TB, Malaria and NTDs
3.4 NCDs –> reduce mortality by 1/3
3.5 ETOH/Drug/Substance abuse
3.6 RTAs –> halve the number of deaths
3.7 Universal Contraception coverage / access to sexual health
3.8 Universal Health Coverage
3.9 Pollution
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3a. Improve Tobacco management
3b. Empower research and development, vaccines, medications
3c. Staff
3d. Early management and recognition of global health risks (e.g. pandemics)
What is the difference between Equality and Equity?
Equality: everyone gets the same help
Equity: help is given out based on need
