Wk 1 - Evidence based medicine

Question 1

RESEARCH ETHICS

i) what is research ethical approval?
ii) name two situations where research requires ethical approval?
iii) name two types of studies that dont need ethical approval
iv) which committee is involved if the participants are NHS patients/staff or work is conducted on NHS sites?
v) which committee is involved if participants are not recruited from nhs/no NHS sites are involved?

Answer 1

i) research ethics governs the standard of conduct for researchers and is provided by a committee - ensures dignits, rights and welfare of human and animal particpants is protected

ii) need ethical approval if study involves animal/humans where you
- gather novel data or info
- create knowledge that can be generalised beyond the participant sample or setting

iii) no need for ethical approve in health improvement studies eg service eval/qual improvement
- clinical auddit (eval service against a benchmark)

iv) if NHS involved - health reasearch authority (HRA)
v) NHS not involed - specific medical school reasearch officer

Question 2

EPIDEMIOLOGY

i) what are the two main types of epidemiological study?
ii) what type of study are case reports, case series, ecological study, cross sectional or prevalence study?
iii) what type of study are case control, cohort, ecological, cross sec
iv) what type of study are clinical trials, preventative trials and community intervention trials?

Answer 2

i) descriptive (amount and distrib in pops, person, space, time) and analytic (test hypoth, identify and quant risk or exposure)
ii) descriptive
iii) observational
iv) experimental

Question 3

EXPOSURE/OUTCOME/PREVALENCE

i) what is an exposure? what may is affect?
ii) what is an outcome?
iii) what is prevalence?
iv) what does prevalence measure? how is it expressed?
v) give three reasons why we might be interested in the prevalence of asthma?

Answer 3

i) exposure is a risk factor for a disease/outcome eg obesity
- can inc or dec risk of disease/outcome

ii) outcome is the disease, condition or event of interest
iii) prevalence is how many people have condition X?

iv) prevalence measures the frequency of ‘cases’ of a disease in a given pop at a specific time divided by the number of people at risk of having the disease at a given time
- expressed as a percentage/proprotion of 1 or a proportion per. unit of the pop (700 in 1000 people)

v) interested in asthma prev - inform a clinical diagnosis, understand risk factors and outcomes, inform prevention and public health interventions, inform service planning

Question 4

TYPES OF PREVALENCE

i) what is point prevalence?
ii) what is period prevalence?
iii) what is lifetime prevalence?

Answer 4

i) point = proportion of pop that has the characteristic at a specific point in time
- eg how many 15 year olds have asthma in brighton now

ii) period = prop of pop that have the charac during a given time period of interest
- eg how many 15 yr olds have had asthma in brighton in last 12 months

iii) lifetime - prop of pop who have ever had the charac in their lifetime

Question 5

CALCULATING PREVALENCE

i) what is the equation used to calc?

Answer 5

number of people who have the disease / number of people at risk of having the disease

Question 6

THE CROSS SECTIONAL STUDY

i) what is it?
ii) how is the sample selected?
iii) is it descriptive or analytic?
iv) give three strengths and three weakenesses

Answer 6

i) a defined population is surveyed to measure a variable of interest
- takes place at a single point in time and considers several characs at once

ii) sample selected using inc and exclusion criteria

iii) can be both descriptive and analytic
- descriptive - point prevelance of asthma in children in brighton
- analytic - point prev of hospitalisation for COVID19 who do and do not have asthma

iv) strength - can compare prev in exposed and non exposed to RF, quick and inexpensive, can be used to inform a hypoth prior to another study type

weakness - not suitable for rare disease, cant seperate cause (exposure) from effect (outcome) as they are meas at same time, cant meas rate of new cases arising

Question 7

SOURCES OF CROSS SECTIONAL STUDY DATA

i) give an example of secondary and primary data
ii) give a pro and con of each

Answer 7

i) primary - collected by researchers directly from main source for the specific purpose eg mortality register, hosp records, census data

secondary - collected by someone else prev for a diff purpose then used by researchers in the spec study eg survey data

ii) primary - pro is control over how variable of interest is measured
con - more expensive and time consuming

secondary - pro is cheap and anon therefore no ethics needed
- con is limited by data already gathered, low accuracy and missing data

Question 8

SUMMARY

i) what is the key study design to establish prevalence?
ii) what is prevalence?
iii) name two bodies that can give ethical approval

Answer 8

i) cross sectional study is key to establish prevalence
ii) prev = number of people in a pop with a condition at a given point in time
iii) NHS or HRA