Evidence based dentistry Flashcards

Question

difference between odds and risk ratio

Answer 1

OR only approximates RR when the outcome is rare - OR tends to overestimate - the RR as in this case

Answer 2

Confidence intervals quantify the level of uncertainty for the population of interest Sampling introduces uncertainty, don’t know how will affect rest of population

Answer 3

A confidence interval tells us the range of values that a true population treatment effect (e.g. RR) is likely to lie (subject to a number of assumptions)

Answer 4

1 “value of no difference” between treatments indicates that - there is insufficient evidence for a difference between the treatment and control group in the population

Answer 5

- Much research is based on weak science - Many results are disseminated too early – trial not fully completed - Is there any science behind the numbers? - How good is the science? - Some research only makes a weak case for the message – be sceptic - Some research makes a strong case Treatments shown to fight diseases in test tubes won’t necessarily translate to humans (bench science in petri dishes, isn’t just a building block to clinical trial which will be benefit to patient) Treatments that work in animals often don’t have the same results in people – Dolly the Sheep – positive benefit in animals may not translate to humans be sceptical about treatments that have only been proven in animal or lab studies

Answer 6

Researchers watch what happens to a group of people - A group of patients has disease A and is treated with drug X - No control group The researchers observe how many get better - No intervention - Has the treatment caused them to survive or something else attributed?

Answer 7

Cohort or case control - Treatment better than control group – shows treatment may be beneficial Researchers observe what happens to people in different situations-without intervening

Answer 8

patients randomly split into 2 groups-one gets intervention the other placebo (TAU) splitting into 2 groups randomly – equal chance of being in one group or the other Any differences at follow-up caused by intervention

Answer 9

- systematic reviews and meta analysis - randomised controlled trials - cohort studies - case-control studies - cross-sectional surveys - ecological studies - case series and case reports - ideas editorials and opinions higher: experimental interventions lower: observational, non-interventional

Answer 10

A report on a single patient or series of patients with an outcome of interest - No control group is involved

Answer 11

- Cannot demonstrate valid statistical associations | - Lack of control group

Answer 12

The observation of a defined population at a single point in time (or time interval) snapshot Exposure and outcome are determined at the same time - Can see relationship which may be incorrect as collected at one point e.g. asthma and smoking (cannot determine what came first)

Answer 13

- Estimating prevalence of a disease e.g. caries in Scottish schools - Investigate potential risk factors – can’t say actual link as cannot measure prospectively

Answer 14

- Identify new disease outcome e.g. when e-cigarettes issue arise, drug for morning sickness in 70s - Hypothesis generation a hunch/feeling of a link, lead onto a trial

Answer 15

- Causality - Confounding – measure one thing but other factors contribute e.g. healthy diet, less likely to smoke, more exercise etc - Recall bias - inaccurate

Answer 16

The study of people with a disease and a suitable control group of people without the disease - Looks back in time at exposure to a particular risk factor in both groups - retrospective is most common, look back at previous exposures See if a higher prevalence between case and control group of risk factor

Answer 17

looking at potential causes of disease

Answer 18

- Confounding - Recall /selection bias - Selection of controls differences between clinicians decisions = Time relationships (did exposure occur before disease? Didn’t can’t have caused it) See if a higher prevalence between case and control group of risk factor - Well conducted is excellent but hard to carry out Rare disease is hard to recruit (need a huge population to identify cases) - Recruit and look back retrospectively

Answer 19

Establish a group of individuals in population - Measure exposures (through questionnaires, examinations etc) - Follow up over a period of time Identify those that develop disease (outcome of interest) –not know at start what you are going to capture e.g. 1990s baby cohort captured obesity crisis Measure as exposure happening and measure at event so not relying on recall bias – good but time and labour expensive

Answer 20

Estimating incidence of disease – number of new cases of disease over a period of time that has developed Investigating causes of disease – when disease and exposure occurred is recorded Determining prognosis Timing and direction of events – understand when things may have caused disease

Answer 21

- Controls difficult to identify - Confounding - Blinding difficult - For rare diseases- need large samples - Very expensive and time consuming

Answer 22

Sometimes referred to as a Clinical Trial RCTs considered the gold standard study design - For effectiveness and efficacy - Provides strongest evidence on effectiveness of treatments Particularly useful for clinical studies – need to see for grounds on changing practice - Measure baseline of groups before trial Small groups as can’t afford large groups and wouldn’t be ethical

Answer 23

Specification of participants (inclusion/ exclusion criteria) Control/ Comparison groups – what will be difference between groups Randomisation – allows to separate groups fairly and randomly that can be compared – difference are random, equality across groups so only treatment criteria Blinding/ Masking – administrator, patient and analyser don’t know the different groups

Answer 24

Age – very young or old have slightly different physiological factors so may not be appropriate to include Disease severity/ diagnosis Unambiguous – 100% clear in criteria - Exact definitions How you will know if the results of the trial are relevant to your patients

Answer 25

Existence of a comparison group - Placebo - Current standard treatment (TAU) Why? - People often get better on their own Need control to compare – what would happen without treatment

Answer 26

How participants/ subjects/ patients are allocated to treatments. - To minimise Bias Assign participant to one of the two groups - Researcher nor participant has influence over allocation Randomisation should be performed by computer, not up to people as easily manipulated (minimise bias and influence on results) Only systematic difference between the arms of a trial are the treatments themselves

Answer 27

because selectively choose to make drug look favourable

Answer 28

because want treatment

Answer 29

Each individual entered into trial has equal chance of being allocated to any treatment arm (paracetamol / placebo)

Answer 30

A technique used to prevent selection bias by concealing the allocation sequence from those assigning participants to intervention groups, until the moment of assignment. Allocation concealment prevents researchers from (unconsciously or otherwise) influencing which participants are assigned to a given intervention group.

Answer 31

researchers from (unconsciously or otherwise) influencing which participants are assigned to a given intervention group.

Answer 32

If the participant or researcher is aware of which treatment is given this may influence the results - look, taste, smell, action be the same – no difference needs to be blind to: - Participant - administrator of treatment - Assessor of outcome - Data analyst

Answer 33

Provide strongest and most direct epidemiologic evidence for causality

Answer 34

More difficult to design and conduct than observational studies - ethical issues - feasibility - costs Still some risk of bias and generalisibility often limited Not suitable for all research questions – pregnant women, elderly generally excluded Non-blinded RCTs may overestimate treatment effects e.g. estimates of effect from trials with inadequately concealed allocation have been 40% larger than clinical trials with adequately concealed random allocation

Answer 35

Participants are recruited to a study and followed up over time Exposures and disease are measured prospectively - No intervention – don’t manipulate end point - Start with anyone and follow

Answer 36

Participants are allocated by chance to different interventions and followed up and outcomes assessed

Answer 37

Description of the medical history of one or more patients

Answer 38

Observational study that analyses data collected from a population, or a representative subset, at a specific point in time - Survey - No longitudinal aspect - No intervention/trial

Answer 39

All the evidence for RCTs looking at effectiveness of a particular treatment are synthesised

Answer 40

People with a disease (cases) are matched to those without it (control) and earlier exposure to different factors are compared - Start with outcomes – look back at exposures (get association) - Quicker as already have outcomes - Can’t assess prevalence in population

Answer 41

variety of study designs may be appropriate for a particular clinical question, need to use the Evidence Levels pyramid / table and question the feasibility of conducting such a study to determine what is most appropriate.

Answer 42

inclusion/exclusion criteria comparison/control randomisation blinding