EBP Flashcards
1
Q
Five stages of evidence based practice
A
1 .convert the need for info in an answerable question
2 .find the best evidence to answer this question
3 . Critically appraise the evidence
4 . Apply evidence to the patient
5 . Evaluate your effectiveness and efficacy at step 1-4
2
Q
Definition of EBP
A
EBP is the conscientious (careful) explicit and judicious use of current best evidence in helping individual patients make decision about their care in the light of their personal values and beliefs
3
Q
What information can be found in guidelines
A
Usually based on 1 disease and describe : Diagnostic criteria Investigations Immediate treatment Subsequent treatment Monitoring treatment Discharge policy
4
Q
When to use guidelines
A
Good enough quality AND
Relevant to your patient
5
Q
Who produces guidelines that i can trust
A
NICE
SIGN- Scottish intercollegiate guiltiness network
6
Q
How do I apply that information to my patient?
A
Best external evidence: guidelines -the stronger the evidence recommendation, the more weight this should be given
Individual clinical expertise : think about co- morbidities (guidelines usually only consider one disease)
Patients values and expectations
EBP
7
Q
Evidence can come from
A
RCT
Meta analyses
Cohort studies
Case control studies
8
Q
What’s the purpose of clinical trails
A
Designed to determine efficacy
Collect efficacy and safety data on new drugs
9
Q
After which point does patient irreversibly stay in clinical trail?
A
After they have given consent
Before allocate to trt
10
Q
What’s parallel group design
A
Treatment gp and control gp run in parallel
11
Q
What does inclusion and exclusion criteria affect?
A
They affect the extent to which the results of the trail can be generalised
12
Q
Randomisation is viewed as gold standard because?
A
Possible error is just chance
13
Q
Randomisation avoid … bias
Benefit
A
Avoid allocation bias
Comparable groups with respect to measures and unmeasured risk factors
Eliminates confounding- trt is independent of outcome
Equipoise
14
Q
Chi square
A
How likely it is that an observed distribution is due to chance
15
Q
Double blind is ideal cause
A
It protects against information bias
Neither patient nor/or(if single blind) researcher knows the trt being taken
16
Q
Study power =
A
Probably of detecting a true difference (usually >80%)
17
Q
What is primary outcome
A
The outcome that the trial is designed to investigate
18
Q
What is secondary outcome
A
Other outcomes that are of interest for example symptom relief, adverse events,quality of life
19
Q
What is clinical endpoint
A
It reflects survival or symptomatic status of patient
20
Q
What is Surrogate endpoint
A
Associated with clinical endpoint but do not directly reflect survival or a clinical status
Example: BP, cholesterol, tumour size
21
Q
Non randomised method
2 types of control
A
Historical control - use the control from literature /databank and compare it with new drug group
Concurrent control - control gp at one centre, trt gp at another / same centre
22
Q
Pros and cons of crossover design
A
Pros - eliminates between subject (person) variation from trt comparisons
- make more use of each subject
Cons- more complex
Difficult to interpret carry over (left over trt A + trt B) is present
Consequence of drop outs more serious
23
Q
Date collection (when? What for? Types? Other purpose
A
Baseline date - prior to start of trt
Efficacy
Safety data - non/ serious ADR
Follow up status
24
Q
Intention to treat -?
A
All subjects inc regardless of adherence
All outcomes must be determined of whether the trt has been discontinued
25
Objections to ITT
| And response to objections
Sub who discountinue no longer receive the benefit from the trt
ADR occurred after trt stopped bias analysis
Study may lack of power where nonadherance is significant
Non adherence can be beneficial in non inferiority or equivalence trail
Non adherends reflect real-life usage
Excluding subject would produce biased estimates
26
Per protocol analysis
Include only those events that occur while participant is complying with intervention
Vulnerable to bias
27
Non inferiority design is
To evaluate new trt is not inferior to stnd trt ( less toxic?)
Trail design is more challenging
28
Terms used to Describe disease frequency
Incidence
| Prevalence
29
What's incidence
Measure of occurrence of new cases of disease
30
Incidence rate is equation
No of new cases of disease / mid year population -only inc those "at risk" of getting the disease
31
How to calculate incidence rate that take changes in population into account?
Number of new case / disease- free person-time at risk
| 2 case/ 24person- years
32
For dynamic population how to calculate incidence rate
The no of new case of disease within a specific time period (person-years: add up the years that each person lived for, when the test is carried out
33
Comparing incidence rates between calendar years can be misleading if the population structure has changed (ppl get old) What are the ways to overcome it
Standardisation -reduce distortion in the rate comparison
Compare rates by categories e.g. Age
Stratify -form into groups
34
Incidence is new case of disease but prevalence is focused on
Disease status
35
What's point prevalence
The proportion of ppl who have a disease at a specific POINT in ti
time
36
Period prevalence
The number of ppl who gave the disease in a time period divided by the population at mid- point of the period
37
What's the equation for prevalence
Number of cases / number of people in the population
38
Prevalence will always be between .. and ...
0 and 1
39
Prevalence depends on two factors
Disease incidence
| Duration
40
Prevalence may change over time with
Changes in incidence
Changes in disease duration
Intervention programmes
Changing classifications
41
What's relative risk
| How to calculate it
The ratio of risk between incidence (exposed gp) and incidence (unexposed gp)
Exposed outcome/(EO+exposed no outcome-total population)
Divide by
Unexposed outcome/ (UO+UNO)
42
What's is risk?
Probability that individual WILL BE diagnosed with outcome over follow up period
43
What does it mean when RR=1
There is no difference in incidence exposed and unexposed
44
Measures of variability
Standard deviation qualifies...
Used for ...
Quantified spread of a set of individuals in population
| Used for description
45
Stand error quantifies...
Describes
Used for...
Spread of sample means
Precision of means
Estimating and calculate confidence interval
46
How are populations selected in a cohort study
People WITHOUT the disease being studied
47
2 ways to measure an effect give examples for
Absolute
Relative
Absolute risk difference, Attributable risk , NNT, NNH
Relative risk, risk ratio, hazard ratio, odd ratio
48
How to calculate attributable risk
=absolute risk reduction
| Incidence exposed - incidence unexposed
49
What does NNH measures?
The ADR impact of a trt
| The no of ppl who when treated results in one additional harmful outcome
50
How to calculate NNH?
| Results should be round up/ down?
1/ absolute risk difference
| Always round down the nearest while number
51
what's NNT
No of ppl who must be treated with new trt to achieve one more success than an old trt
52
What does it mean when NNT=1
New trt always effective
53
How to calculate NNT
1/ absolute risk difference
54
Hazard means
The risk of getting outcome in following short time interval (given that outcome has not already occurred)
55
Hazard can quantify ...
Differences in survival
56
What's hazard ratio?
| Will it be constant over time?
Compare hazards bw gps over follow up time
| Hazard may change but hazard ratio is constant
57
What's confidence interval
A range of values which we can be confident includes the true value (e.g. Point estimate
58
How to calculate 95% confidence interval
Mean+- (1.96x SE)
59
What does SE represent
| SD?
The variability of sample MEANS
| Variability of a population
60
Definition of 95% confidence jntervak
If you repeated the study 100 times, on 95 of those times the point estimate (mean) will be within the confidence interval
61
Point of no difference for absolute and relative difference when value is no difference to interval
Absolute =subtraction so 0
| Relative division so 1
62
Definitions for null hypothesise
| Alternative hypothesis
Null: there is NO DIFFERENCE in outcomes comparing treatment with no treatment
Alternative: there is A DIFFERENCE
63
Definition of p value
Probability of HAVING OBSERVED our data or more extreme data when the NULL HYPOTHESIS IS TRUE
64
P=.... is usually the value to compare p values against
0.05
65
How to work out SD
```
Root mean square
Work out mean
Mean - value , square it
Add up the square values
Divide by no of values - mean
Square root the mean
```
66
What fixed/ open cohort studies
Fixed- exposures are defined
New subjects not included
No movement bw gps
Open- movement can occur in and out of the cohort
67
Hills aspects of association (for causation of disease)
CSS -consistency strength of association specificity
BBC -biological gradient and plausibility coherence
EAT - experimental evidence analogy temporality
68
Limitation and use of large simple trails
Reduced the info collected to the minimum required to test hypothesis
Used to test the risk of ADR
69
Is observation studies experimental or non experimental
Are there any control over exposures/ population
Can confounding occur
Non experimental - no risk to patients
No control over exposures assigned but can select subjects included
Confounding can occur
70
Steps in the design process of case control study
```
Define research question
Design study
To find - group of interest (cases)
- comparison group (controls)
Take histories (identify exposures)
Analyse results
Draw conclusions
```
71
RCT- 4 aspects of measuring outcomes
```
Unequivocal (no doubt) death
Measured BP, hba1c
Clinical assessment (objective) swollen joints, X-ray results
Patient opinion (subjective) pain, s/e
```
72
In parallel group design for non randomised trail -may have a run-in period
Patient presents - eligibility - consent -run in then -(irreversibly) allocate to trt
Test tolerance to cardiac suppression drugs
Determine disease stability e.g. Copd
Test patient adherence to intervention
Ensure zero plasma level of old trt
73
Case control study-what cases should be included
Cases with outcomes of interest
74
CCS- controls - are there any req?
Controls should be found from hopstial neighbourhood community
75
CCS- match and unmatched studies can be used to
| Often match on .. and ...
```
Overcome confounding ( males more likely to have MI)
Match on age and sex
```
76
Odds:
Probability of event occurring divided by probability of event not occurring
77
Odds ratio:
| How to calculate:
Compares odds that an outcome will occur, between exposed and absence of exposure groups
Odds of exposure in case and control gps
OR= odds of CASES having exposed/ odds of CONTROLS having exposed
A/C (a- cases exposed, c- cases unexposed)
Divided by
B/D (b- control exposed, d- control unexposed)
78
```
Cohort vs case control studies
Population sampling-
How to obtain data -
Exposure / event status known or unknown-
Compare results -
Analytic calculation-
```
Cohort: Take a gp from population who do NOT have the outcome of interest / case control: take a gp WITH outcome of interest (cases)
Follow them forward in time see what happens/ retrospectively (consider past exposure) identify an appropriate comparison group
EXPOSURE is known / EVENT STATUS is know
Compare OUTCOMES in exposed and unexposed gps/ compare EXPOSURES in case and control
Calculate RELATIVE RISK/ calculate ODD RATIOS
79
What is p value
Probility of finding the observed, or more extreme, results when the null hypothesis is true (results is due to chance)
80
What tools help you to critically appraise?
| How many other tools are there?
CASP- critical appraisal skills program
| 7
81
What does PICO stand for
Population
Intervention
Comparator
Outcomes
82
What is alpha level
Is the significance level - probability of making wrong decision when the null hypothesis is true
Usually use alpha level 5%
83
What's bias
It can be in terms of
Can result in ... risks
Systemic error in data/ study
At the pint of study design
Cannot be eliminated at point of analysis
In terms of selection of study subjects, exposure classification, outcome classification
Over/ underestimated risks
84
Misclassificarion have 2 gps
Non differential - misclassification to same degree for all groups
Differential- misclassifcation different between groups
85
Confounding
The distortion of RISK ESTIMATE due to the mixture of the ppl in the study population
86
Confounder
A confounder is a RISK FACTOR for the disease and is CORRELATED with the EXPOSURE INDEPENDENT OF DISEASE
87
How to control confounding?
| Can be implemented at design and analysis stage
```
1 randomisation
2 restriction
3 matching
4 statified analysis
5 multivariate analysis
RRMSM
```
88
Two ways of analysis of data to control confounding
Stratified analysis- separate out factors, so any mixture of their effect is removed, used for 1-2 factors
Multivariate analysis - take into acc of annulled of factors
89
Methods to search a paper for systemic review
```
1 define the question PICO
2 identify search terms
3 use literally searching
4 review papers
5 summarise results
- descriptively for systemic review
- quantitatively for meta analysis ( check for heterogeneity
```
90
Define a standard method for extracting data from a paper in systemic review
```
Need study details (type: cohort/ case control/ RCT)
Location
No of patient included
Patient demographics
Exposure
Covariates
Overall result
```
91
When to do a systemic review when to do a meta analysis?
Descriptive summary - systemic
| Results can be combined and quantified - meta analysis
92
What type of Meta analysis to use when variation is due to sample variation only?
If there is heterogeneity
Fixed effect meta analysis
Examine this assumption using a test of heterogeneity
Then use a Random effect meta analysis
93
What is marginal utility?
In economics, decisions are made at the margins i.e. At the point when the utility (satisfaction) not 'worth' the 80p you spend
Marginal utility- at the margin of your satisfaction (about to become unsatisfied)
94
What is opportunity costs
You have less resources (money, time) to do things (opportunity)
95
What is health economics
The study of attempts to allocate limited health care resources among unlimited wants and needs to achieve the max health benefit for society
96
What is pharmacoeconomics
The application of the theories, techniques and concepts of health economics to the study of pharmaceutical interventions (treatment)
97
Medicine regulations QSEC
Quality
Safety
Efficacy
Cost effectiveness
98
What's is economic evaluation (in term of pharmacoeconomics)
Comparison of two or more alternative treatments in terms of costs and consequences
Quantify the differences
Ensure max utility from scares resources
99
What's QALY
Quality- adjusted life-years
| Number of years lived x utility
100
What can be used to measure the QOL for all health conditions?
EQ-5D scores
Compare with state values
Gives a utility scores between 0 (worst state) and 1
101
Different types of economics analysis CMA
1 cost minimisation analysis - assume effectiveness is equal,
compares cost of trt with two or more drugs/ interventions
Whichever gives desired outcome at the LOWEST price is preferred
102
Different types of economics analysis CEA
Cost effectiveness analysis
- NO assumption on equal effectiveness
-Benefit = non monetary terms (usually QALY)
-the greatest effectiveness for the lowest cost
- only consider NHS costs
- main measure in CEA is the ICER
ICER= C1-C0/ E1-E0
C1,E1 the cost and effect in study trt group
C0,E0 the cost and effect in study control group
103
how to calculate ICER
Compare two different trts
Diff in treatment costs/ diff in effectiveness
Additional cost for each additional patient effectively treated
104
Different types of economics analysis CBA
Cost -benefit analysis
To compare the outcomes of a medical intervention expressed in monetary terms - not easy so use
Willingness to pay approach (assign monetary value to health consequences)
How much you like to pay for additional 2 yrs of life? (Depends on the age)
105
Economics is about how to make choices ...
Make choices in the context of scare resources
106
Economic decision are made at the .....? What the outcome of interest
Margin
| The incremental cost effectiveness
107
Incremental analysis
Assessment of the relative cost and the benefit of each marginal addition or reduction in production or consumption
108
What's the CEBM levels of evidence
The centre for evidence based medicines
109
CEBM - does this trt help?
```
Level 1 (best) systematic review of RCT
2 RCT OR observational study with dramatic effect
3 non Randomised controlled cohort/ follow up study
4 case series, CCS, historically controlled studies
5 mechanism- based reasoning
```
110
CEBM - what are the common harms?
1 systematic review of RCT or Observational study with dramatic effect
2 RAndomised trail or ob study with effect
3 non randomised CT/ follow up study
4 case control studies, historically CS
5 mechanism- based reasoning
111
CEBM- graded may go down on basis of :
| Grade may go up if
Study quality
Imprecision of result ( large 95CI)
Indirectness (study PICO not question PICO)
Absolute effect size is small
- there is a large effect size
