Epi Surveillance Flashcards
Systematic Review
List and explain 5 criteria that you would use to evaluate the quality of a new systematic review on the health harms of e-cigarette use in adults.
- Did the review questions and inclusion criteria define the population, intervention, and outcome
- Did the review use a comprehensive search strategy and provide appropriate details?
- Were the methods established prior to conducting the review?
- Did the review provide a list of included and excluded studies with justification and adequate details?
- Did the review authors use a satisfactory technique to assess the risk of bias in included studies?
Qualitative Methods
Increasing rates of syphillis have been reported in many MSM populations in Canada. Describe 3 qualitative research data collection strategies and provide examples which might be used to try to identify reasons for increasing rates of unprotected sex in this group.
- group interviews - ex. focus group. Group of people are asked about their perceptions, opinions, beliefs, in an interactive group setting where participants are free to talk with other group members.
Example - interview with a group of MSM individuals to discuss barriers to protection during sex - individual interviews - ex. Key informant interview
in depth 1:1 conversations
Example: in depth discussions in 1:1 setting with single cases - Ethnographic (ex. observation) - researchers interact with participants in real life settings to understand behaviour drivers.
Example: researchers go to nightclubs and observe how individuals approach meeting new partners and availability of safer sex educational material and products (i.e. accessibility of condoms)
Qualitative Methods
List three types of qualitative research data collection strategies and advantages and disadvantages of each one
1) group interviews - ex. focus group.- group of people are asked about their perceptions, opinions, beliefs, in an interactive group setting where participants are free to talk with other group members.
Advantage: individuals can interact with another during the setting and generate group based insights
Disadvantage: Social desirability (individuals expressed views may differ from actual views due to presence of other and pressure to conform)
2) individual interviews - ex. Key informant interview
Advantages:
Disadvantage:
One of the main criticisms is that the data collected cannot necessarily be generalised to the wider population.
3) Ethnographic (ex. observation) - researchers interact with participants in real life settings to understand behaviour drivers.
Advantage: Can help identify unexpected issues that the researchers did not know to ask about
Disadvantage: costly time intensive, and in certain circumstances not feasible for ethical or privacy reasons
What are 6 steps of a systematic review
Framing the Question
Develop a study Protocol
Identifying the Relevant Work
Assessing the Quality of Evidence
Summarizing the Findings
Interpreting the Evidence
https://www.lib.uwo.ca/tutorials/how_to_perform_a_systematic_review/index.html
You are a provincial health consultant who is in charge of a new screening program for a cancer. What are 5 adverse effects that can occur from screening?
- False Positives: individual tests positive without disease and experiences further invasive procedures or treatment
- False Negatives: Individuals tests negative for disease even though they have it potentially resulting in delayed care or interventions
- Stigma: individuals who screen positive may experience stigma due to nature of condition
- Over-diagnosis: individuals screen positive for the disease or condition but would never have experienced symptoms or premature mortality from it
- Increased health inequities: participation and benefits from the screening program are not distributed in an equitable manner resulting in widening disparities.
List three types of bias when evaluating a screening program that may result in the appearance of increased benefits
Lead time bias - individuals identified through screening program are found earlier in disease course that those diagnosed without screening but do not survive longer from disease onset
Length time bias - screening is more likely to detect individuals with a slowly progressing from of disease compared to more aggressive disease
Selection bias - individuals who participate in screening program may be healthier, better lifestyles, and more likely to adhere to therapy.
Define a cross sectional study design
An observational study where exposure and outcomes are assessed at a single point in time.
List 3 strengths and 3 weaknesses of cross sectional study design
Strengths:
- Inexpensive
- Quick
- Can assess multiple exposures and outcomes
- Can calculate prevalence
Weaknesses:
- Cannot assess time trends
- Cannot assess causation
- Difficult to assess rare outcomes
What is the key difference between a cohort and case control study
In a case control study the outcome is known and the exposure status between cases and non cases is investigated, in a cohort study the exposure is known and the outcomes in the exposed and non exposed groups are investigated
When can an odds ratio be considered equivalent to a relative risk
When the outcome is relative rare in the investigation (<20%)
If the odds ratio is interpreted as a relative risk it will always overstate any effect size: the odds ratio is smaller than the relative risk for odds ratios of less than one, and bigger than the relative risk for odds ratios of greater than one
A recent study examined the association between avoidable mortality and neighbourhood marginalization. The study took neighbourhood marginalization (a continuous variable) and divided it into quintiles. What are
3 limitations and 3 benefits of this approach
Limitations
- reduces ability to compare results between studies in different settings as quintiles may not represent the same exposure in different regions (analagous to comparing two studies on the association between poverty and health, when poverty was defined as an annual income of $22,000 in one and $47,000 in the other)
- increases liklihood of false positive due to multiple testing
- assumption that risk is homegenous within each category (i.e. within lowest quintile bottom 5 percent might be very different than next 15 percent)
Advantages
- Facilitates communication to the lay public and decision makers
- Can be easily used to divide groups into levels of risk
with a relative risk for each group - facilitates interpretation of statistical interaction (effect measure modification) tests (interactions between continuous variables are difficult to interpret)
What is the difference between direct and indirect standardization?
What data do you need to do direct standardization?
What data do you need to do indirect standardization?
Direct Standardization
- Uses the age structure of a reference population and the known event rates by age or sex in two populations to create standardized rates
- need the number of events and the number of individuals in the population for multiple age ranges in two separate populations
Indirect Standardization
- Uses the known age specific rates of a reference population to calculate the expected overall number of cases in the population of interest
- need to age specific reference rates and the observed number of cases / number of individuals in a population for 1 population
What are essential components of a surveillance system?
- – What is the population under surveillance?
- – What is the period of time of the data collection?
- – What data are collected and how are they collected?
- – What are the reporting sources of data for the system?
- – How are the system’s data managed (e.g., the transfer, entry, editing, storage, and back up of data)? Does the system comply with applicable standards for data formats and coding schemes? If not, why?
- – How are the system’s data analyzed and disseminated?
- – What policies and procedures are in place to ensure patient privacy, data confidentiality, and system security? What is the policy and procedure for releasing data? Do these procedures comply with applicable federal and state statutes and regulations? If not, why?
- – Does the system comply with an applicable records management program? For example, are the system’s records properly archived and/or disposed of?
How do you calculate a attributable fraction (attributable risk percent)
If the a study find a an AR of 30% between lung cancer and radon how would you interpret this finding?
AR = Incidence exposed - incidence unexposed / incidence exposed *100
30% of lung cancer cases in individuals exposed to radon are attributable to the radon exposure
How do you calculate the population attributable risk
If the a study find a PAR of 0.02 between lung cancer and radon how would you interpret this finding?
Incidence total population - incidence unexposed
For every 1000 individuals in this population 20 will develop lung cancer due to exposure to radon.
