Epidemiology Flashcards
Confidence interval definition
Range of values for variable of interest with specified probability of including true value of variable.
Usually 95% significant if confidence limits does not cross “no effect value” (eg. Relative risk of 1)
P-value definition
Probability that results observed in a study is due to chance, quantified as a value between 0-1.
<0.05 generally accepted as statistically significant
Number needed to treat
- Formula
- Definition
- 1/ARR (absolute risk reduction)
2. Number of patients who received the treatment to produce ADDITIONAL benefit for one individual.
When to use relative risk
In cohort studies
When describing the POPULATION IMPACT
(When informing patients, more useful to use Absolute Risk)
- Attributable risk formula
- Population attributable risk
- What does attributable risk show?
- (Incidence in exposed - incidence in unexposed) / (incidence in exposed)
- expressed as a percentage - The above “attributable risk” x prevalence in population
- Demonstrates what proportion of a specific disease is attributable to the risk factor. In a population, can indicate potential impact of control measures when studying what impact of the disease in a population is attributable to this.
Random error.
- What is sampling error
- What is type I (alpha) error
- What is type II (beta) error
- Sample error is commonest cause of error, from randomness of sample collection. Reduce by increasing power.
- False association made when there is none. More harmful as we will then try to make interventions. Set p-values to minimise alpha errors (eg. <0.05 chance alpha error will occur, can even go lower)
- No association made when there is one. Can reduce by increasing power
Systematic error (SIC)
- What is Selection Bias
- What is Information Bias
- What is Confounding bias
- Especially happens in case-control studies, where case population does not really match control population
- Wrongly classified into a group. Eg. Case control, the subject may not remember having had been exposed to a certain risk factor and therefore not counted.
- When the conclusion is confused because another exposure has not been taken into account.
6 steps of Priority Setting for implementing a new intervention
- Need - do corporate needs assessment, and all the other ways of needs assessment
- Intervention - critically appraise evidence. 2 problems:
1) PH interventions often multifaceted with confounding factors
2) When evidence states current treatment is ineffective - Acceptable (by target population. Do surveys and
questionnaires etc) - Cost-effective. Think about DIRECT, INDIRECT and OPPORUNITY costs. Also the cost-efficacy, effectiveness, utility and benefit etc.
- Ethically justified? (4 principles)
- Overall justified? (Look back at all the above)
What are the 3 main approaches to developing a health needs assessment?
- Cooperate
- Comparative
- Epidemiological
Comparative needs assessment
- Where is data obtained and what is it used for?
- Advantages?
- Disadvantages
- Local hospitals and GP practices, to allow comparison between geographical areas to be made, and compares with previously set standards
- Data already present, there is an easy starting point
- Data may be old, different hospitals have different admission criteria for the same conditions, misdiagnoses
Corporate needs assessment
- Where is the data obtained, and what is it used for?
- Advantages?
- Disadvantages?
1. "CQFI" = corporate Citizens juries Questionnaires Focus groups Interviews in various settings
- Involves public opinion and gives insight into the other factors that affect health
- Time-consuming to carry out, and require a lot of effort to do these qualitative assessments
Epidemiological approach to needs assessment
- What main questions do they address
- Purpose of epidemiological needs assessment
- Examples of things they look at…
- Large-scale analyses, identifying several issues:
- how big is the problem
- what is currently being provided
- are the current services effective, and can something else be done?
Used for WHOLE SERVICES, such as mental health, coronary heart diseases etc to assess priorities of service provision in these circumstances… - Identify health improvements which can be achieved by reallocation resources in order to remedy over-provision and unmet needs.
- Whole specialties (eg. Mental health)
Diseases (eg. Coronary heart disease)
Client groups (eg. Alcoholics)
Vulnerable groups (eg. Ethnic minorities)
What are the 5 main stages of a policy-making/ planning cycle.
- Assess health status
- Identify problem and prioritise
- Identify options for solutions
- Choose one solution
- Implement this service, with consultation by material providers etc.
- Evaluate and monitor
- Repeat
Crude death rate definition
Total deaths / 1000 / YEAR
Directly standardised death rate
- “Definition” and method
- Disadvantages
- Death rate that would have occurred in the REFERENCE population if it had same age- and sex- specific deaths the study population
- Tedious to construct, as would need to standardise all the different sex or age groups in every study population to compare to reference. Easier just to keep ref population as a standard, and compare with all the other populations
What is indirect standardisation and SMR?
What does it used for?
Definition of SMR >/< 100
- SMR = deaths observed in study population group: death rate if it were standardised with same age and sex-standardised as ref population x 100
- Used to compare populations that are differentiated by factors such as geographical, social class eg.
- > 100 suggests study population is doing worse than reference population, and vice versa.
Perinatal mortality rate definition
Stillbirths + within first 28days of life per 1000 LIVE BIRTHS
(Basically is Stillbirth mortality rate + neonatal mortality rate)
Neonatal mortality rate definition
No of deaths within first 28days of life per 1000 LIVE BIRTHS
Early = within first week of life
Late = from 2nd week to 4th week
Post-neonatal mortality rate definition
From 28days to 1y/o per 1000 live births
Maternal mortality rate definition
Death from PUERPERAL causes during pregnancy, and within 42days after birth per 1000 live births
Stillbirth death rate definition
Stillbirths per 1000 total live births
NB. Stillbirth is after 28/40 gestation
Infant mortality rate definition
Deaths at <1y/o per 1000 live births
Basically neonatal and post-neonatal deaths summated
Years of life lost definition
No. of deaths lost before 75y/o, over total population.
Can give some information about causes of death.