Evidence Based Medicine Flashcards
What is the order of levels of evidence?
Systemic reviews Randomised controlled trials Cohort studies Case-control studies Case series, case reports Editorials, expert opinion
What is a cross-sectional study?
A selected sample from the population is divided into:
- Those with the risk factor and the disease
- Those with the risk factor and no disease
- Those with no risk factor and the disease
- Those with no risk factor and no disease
What is a case-control study?
Subjects that have the disease are analysed to determine whether they were exposed or unexposed to a risk factor, and this is compared to controls who don’t have the disease
What is a cohort study?
Study participants with risk factors present are exposed, or not exposed to a factor. The outcome of individuals in each group is evaluated
What is a randomised control trial?
Random - the population receiving the intervention and the population being compared are only different because of random variation
Control - the intervention is being compared to something else: a placebo, a gold-standard, best practice
What is the inclusion criteria for patient selection?
Likely to benefit from treatment - definitely has the disease, likely to respond
Unlikely to be harmed - no known adverse reactions/contraindications
What is the exclusion criteria for patient selection?
Clear preference for intervention or control - by patient or doctor
Patient unlikely to adhere to treatment/complete follow-up
What are different types of control?
Placebo
Nothing
Current best practice
“standard care”
What is confounding?
When the association between an exposure and an outcome is in fact the result of another variable
What is a systemic review?
A review of the evidence available on a question that uses systematic methods to extract and analyse data from studies
What is absolute risk?
The number of events in treated or control groups, divided by the number of people in that group
What are ARC and ART?
Absolute risk of control group (ARC) and treatment group (ART)
What is ARR - absolute risk reduction?
ARC - ART
What is RR - relative risk?
ART/ARC
What is RRR - relative risk reduction?
(ARC - ART) / ARC
What is NNT - number needed to treat?
1/ARR
What is triangulation?
The area under investigation is looked at from different perspectives
What are the 4 phases of clinical trials?
- Clinical pharmacology - determine dosage, safety
- Initial clinical assessment - determine likely effectiveness, common adverse effects
- Rigorous testing - randomised control trial
- Post-marketing surveillance - find less common adverse effects
What should a screening test be?
For an important condition with a recognisable latent or early symptomatic phase
A test that is accurate, simple, safe and precise
For a condition with effective and available treatment
Cost effective
What is sensitivity?
How well the test detects having the disease
High sensitivity = few false negatives
What is the calculation for sensitivity?
Number of results where disease is detected in people with the disease / number of people with the disease x 100
What is specificity?
How well the test detects not having the disease
Highly specificity = few false positives
What is the calculation for specificity?
Number of ‘normal’ results where disease is not detected in people without the disease / number of people without the disease x 100
What is positive predictive value?
How reliable is the test result when it shows disease is present
