EBM Flashcards
What are the four A’s?
Assess, access, appraise, act
What is CASP?
Critical appraisal skills programme.
What is DTA?
Diagnostic test accuracy
What is a predictive value?
The predictive value refers to the likelihood for getting a positive or negative result irrespective of whether that result is right or wrong.
What is meant by a positive predictive value?
True positives / true positive + false positive
What is meant by a negative predictive value:
TN/ TN + FN
What is sensivity?
No. of correct results.
TP/ TP + FN
What is an index test?
The new test to compare with the reference tes
What does a qualitative test do?
Assesses patient experience
What is reflexivity?
Reflexivity generally refers to the examination of one’s own beliefs, judgments and practices during the research process and how these may have influenced the research. it involves drawing attention to the researcher as opposed to ‘brushing her or him under the carpet’ and pretending that she or he did not have an impact or influence. It requires openness and an acceptance that the researcher is part of the research. It also means turning the lens back on oneself and their positionality.
What is positionality?
What we know and understand
What are the stages of thematic analysis in qualitative research?
- Familiarization of data
- Initial coding
- Themes searching
- Reviewing themes
- Naming and defining themes
- Producing the report
What is data saturation?
Data saturation refers to the point in the research process when no new information is discovered in data analysis, and this redundancy signals to researchers that data collection may cease.
What does triangulation involve?
Methods, interventions, sources
What are sources of secondary evidence?
Guidelines
Evidence summaries
Systematic reviews
What is the iterative approach?
An iterative approach is one where the content of the discussion, stimulus, or sometimes even the methodology is adapted over the course of the research programme. … This approach is particularly useful for time-sensitive projects where there isn’t scope for multiple rounds of research.
How are qualitative studies more trustworthy/ valid?
*
- Multiple reviewers
- Justification of inclusion
How is data made credible/ reliable
Showing that all data was analysed
Multiple researchers
What are some key CASP questions for an RCT?
Section A: Are the results of the trial valid?
- Did the trial address a clearly focused issue?
- Was the assignment of patients to treatments randomised?
- Were all of the patients who entered the trial properly accounted for at its conclusion?
- Were patients, health workers and study personnel ‘blind’ to treatment?
- Were the groups similar at the start of the trial
- Aside from the experimental intervention, were the groups treated equally?
Section B: What are the results?7. How large was the treatment effect?8. How precise was the estimate of the treatment effect?
Section C: Will the results help locally?9. Can the results be applied to the local population, or in your context?10. Were all clinically important outcomes considered?11. Are the benefits worth the harms and costs?
What is a sham intervention?
When someone is given something to do or take to make them feel they are taking part.
What is allocation concealment?
Allocation concealment is a different concept to blinding. It means that the person randomising the patient does not know what the next treatment allocation will be. It is important as it prevents selection bias affecting which patients are given which treatment (the bias randomisation is designed to avoid).
What is an ecological study?
Studies in which the units of observation are groups of individuals rather than individuals themselves, for example, populations of different countries, or towns, or health regions/districts.
What are cohort studies?
Cohort studies are studies in which a group of individuals who are defined on the basis of their exposure to a risk factor and are then followed-up over time to determine who develops the disease of interest.
What are the different categories of exposure in cohort studies?
Refinement of measurement of exposure:−dichotomous (ever/never exposed)
−categorical (no/low/medium/high)
−quantitative measured exposure (continuous variable)
What are some of the ways exposure and outcomes can be measured?
record linkage with national electronic databases (e.g. deaths,cancers, hospital episode statistics (HES))−questionnaire to study subjects−clinical examination
What is the equation for relative risk?
a / (a + b)
_____________
c / (c + d)
A - exposed effect. b - exposed no effect
C no exposure effect. D no exposure no effect.
What can be done to reduce confounding variables?
Adjustment for confounding may be achieved by use of standardisation, stratification or use of a suitable regression model.
Define regression model.
A regression model is used to investigate the relationship between two or more variables and estimate one variable based on the others.
How can confounding variables be measured in case- control studies?
Sometimes it may be advantageous to match controls to cases on factors such as age and sex which may confound the relationship between disease and exposure.By such matching we have forced the cases and controls to be similar with regard to the matched factors, which is helpful in controlling confounding, but it is essential to use methods of analysis which account for such matching otherwise the results will be biased.
What is relative risk?
Incidence rate of disease among those exposed to the factor/
Incidence rate of disease amongthose unexposed to the factor
What is the criteria for assessing causality?
Biological plausibility – does it make biological sense
- Time – logically a cause must precede its potential effect
- Strength of association – the stronger the association of an exposure with disease occurrence then the harder to conceive of likely confounders which might explain the association
- Biological gradient or dose-response relationshipCausality as a plausible interpretation is strengthened if there is a strong dose-response
- Consistency – consistent with other studies in different populations, places and times add weight to a cause-effect interpretation
- Specificity – if the supposed cause is associated with one disease only, or the disease is associated with one cause only, can add weight to causal interpretation.
- Coherence – should not contradict what is already known about the natural history and biology of the disease.
- Experiments – occasionally natural experiments offer themselves, such as tap-water fluoride levels and specific disease outcomes.
- Analogy – very rare and potentially dangerous
Significant difference
If the RR (the relative risk) or the OR (the odds ratio) = 1, or the CI (the confidence interval) = 1, then there is no significant difference between treatment and control groups.
If the RR >1, and the CI does not include 1, events are significantly more likely in the treatment than the control group.
If the RR <1, and the CI does not include 1, events are significantly less likely in the treatment than the control group.
Significant difference
If the RR (the relative risk) or the OR (the odds ratio) = 1, or the CI (the confidence interval) = 1, then there is no significant difference between treatment and control groups.
If the RR >1, and the CI does not include 1, events are significantly more likely in the treatment than the control group.
If the RR <1, and the CI does not include 1, events are significantly less likely in the treatment than the control group.
What does MESH stand for?
Medical subject headings
What is a truncation for search terms?
Where only the first part of the word is written and then asterix e.g. (smok*) - smoker, smoking
What is a wildcard?
It is where the spelling can vary e,g. skiing or skeeing
What is grey literature?
It doesn’t fit into standard medical data bases
What are the limitations of the hierarchy of evidence?
Doesn’t really encompass DTA or qualitative research
RCT may not be done well vs cohort
Randomisation may not be possible due to ethics
What type of error is bias?
A systematic error
What are consort diagrams?
Used to show different arms of a trial
What is a cross-over trial?
One where everyone gets all treatments
For each of these is it prospective or restrospective?
a. Cohort
b. Case control
c. RCT
a. prospective
b retrospective
c. prospective
What are cohort studies?
Studies that follow a particular population to see what happens to them e.g. develop disease or not
What are case control studies?
Observational studies that restrospectively look at two different groups and compare them for exposure
What is a nested study?
When pepople are already involved in a study
What is spectrum bias?
Case mix or population size
What is PPV vs sensitivity?
Positive predictive value is the number of positives that are correct. Sensitivity is how often a test will pick up the disease.
Grounded theory
Is theory building. Coding, thematic pooling and analysis
What are some of the ways of reducing bias in qualitative studies?
Triangulation - using multiple resources
Another researcher
Respondent verification
Reflexivity
What is the Hawthorne effect?
Where people know they are being watched and change their behaviour
What is the Pygmalion effect?
Robert Rosenthal and Lenore Jacobson’s study showed that, if teachers were led to expect enhanced performance from children, then the children’s performance was enhanced.
[cohort observational bias]
What is Cochran’s Q or I2 number a measure of?
Heterogeneity in research
What is attributible risk the same as?
https://www.psychiatrist.com/jcp/assessment/research-methods-statistics/understanding-relative-risk-odds-ratio-related-terms/
Risk difference
Absolute Risk Reduction (ARR); the NNT is the inverse of the ARR: NNT = 1/ARR Where ARR = CER (Control Event Rate) – EER (Experimental Event Rate). NNTs are always rounded up to the nearest whole number.
What’s the Jadad score?
A way of showing randomisation
What is the per protocol effect?
The per protocol analysis, sometimes known as an “on treatment” analysis, included only those participants who complied with the trial protocol. Specifically, it included only those who adhered to the treatment protocol that they were allocated to and provided sufficient data for assessment of the outcome measures.
Whar is PADS?
Performance, attrition, acquiseineces, detection, selection bias
What is generalisability>
Applied
What does CONSORT stand for?
Consolidated Standards of Reporting Trials
What is diagnostic purity bias?
When the tested population is different to the general population because of the inclusion and exclusion criteria
To summarise a paper you should include:
- Objective
- Methodology type
- Population
- Intervention
- Comparator
- Outcome
- Results
What is Non-contemporaneous control bias?
Bias using a historical control
What is SIGN?
Part of GCSO. It is Scottish intercollegiate guidelines network
What are the four key research topics?
Who is affected? Observational
How accurate is the test? DTA
Does an intervention or service work? RCT
Patient experience. Qualitative
What is Neyman bias?
Where the population is either very sick or very healthy and does not reflect values
How is accuracy calculated?
Accuracy = (True Positive + True Negative)/n.
Area under ROC
Grade down?
Risk of bias
Imprecise
Indirect
Inprecision
Publication bias
GRADE up?
Bradford Hill
Dose response
Large effect
