Week 5 Flashcards
define inference
an educated statement about an unknown population
define causal inference
conclusion made about a population from the study of a sample of that population
(determine if effect was caused by association or a direct effect)
define critical appraisal
A systematic process used to identify the strengths and weaknesses of a research article in order to assess the usefulness and validity of research findings
what are examples of objective outcomes related to patients?
delayed or reduced rates of death (mortality)
reduced disease incidence (morbidity)
what are examples of subjective outcomes related to patients?
Symptom relief
Emotional/Mental/Physical Functioning
Health-Related Quality of Life
(all based on scales or scores)
T/F experiments with subjective outcomes are more difficult to repeat and are thus more reliable
false, less reliable
what are examples of continuous data objective outcomes?
lab values
blood pressure
weight
(these outcomes can highly vary… BP can change continuously)
what are examples of nominal data objective outcomes?
death
has the patient had an MI
(these outcomes cannot revert back… a dead pt will not become alive)
what question should be asked in regards to the reliability of subjective information?
has minimal clinically important difference (MCID) been established?
what is minimal clinically important difference (MCID)?
you must determine if the data is actually important. just because it may be statistically significant does not make it clinically significant. for example: a change in BP of 5 could be considered statistically significant, but as clinicians we are able to determine that BP highly fluctuates and we cannot immediately conclude that the change in BP was due to a studies intervention
Subjective outcomes assessed with surveys & scales need to establish?
validity, reliability, and minimal clinically important difference
define what a surrogate endpoint is
A laboratory measurement or physical sign that is used in therapeutic trials as a substitute for a clinically meaningful end point that is a direct measure of how a patient feels, functions, or survives, and that is expected to predict the effect of therapy
explain an example of a surrogate endpoint associated with diabetes
if we are doing a study on how insulin medication benefits patients with diabetes, the true clinical outcome that we care about is reduction in death due to use of insulin. a surrogate endpoint can be used instead to try and show significance of a drug’s benefit. For example, we can measure a patients HbA1C after insulin treatment or fasting glucose after insulin treatment to see insulin’s impact on these factors. These factors are ASSOCIATIONS with insulin use, but are not CAUSATIONS showing insulin’s direct impact on mortality.
what’s another example of a surrogate endpoint associated with osteoporosis?
a clinically meaningful endpoint in regards to osteoporosis is incidence of fractures. a surrogate endpoint could be associating bone mineral density values with the risk of fracture
what are the advantages of surrogate endpoints?
Smaller sample size; expose fewer patients
Shorter trials / faster to market
Easier to measure
Less invasive for patients
what are the disadvantages of surrogate endpoints?
Trial too short to evaluate long-term side-effects
Patients don’t relate their clinical experience to surrogate
Intervention may affect surrogate endpoint but not clinical outcome
T/F surrogate endpoint evaluation cannot be established with a single RCT
true
T/F surrogate endpoints usually show clinical relevancy for patients
false
what does it mean to say that a surrogate endpoint must determine clinically relevant levels of change?
the surrogate endpoint must be able to prove that it is clinically relevant towards the true outcome in order for it to be considered clinically significant (ex. a drug that on average decreases BP by 10 was determined to reduce CV death by 10%)
define composite outcomes
explain its use with an example
a collection of multiple outcomes combined into one outcome
an outcome such as CV death has numerous variables attributing to it and can be caused by numerous variables (MI, stroke). A composite outcome study studies the occurrence of these variables to determine how the drug of interest reduces said variables to overall reduce CV death
what are components of a composite outcome study that are required to show significance?
-the variables in the study must be associated with the true outcome (incidence of MI and GI bleed are not associated with the same outcome)
-the components should be similarly important (asthma-related death & administration of an oral corticosteroid are not related to each other)
- the incidence should be similar for all components
-the treatment effect should be similar for all components (similar risk ratios)
what are the 4 key components of the critical appraisal of studies?
-validity
-reliability
-importance
-applicability
what is internal validity?
validity within the confines of the study methods: does it appropriately test/measure what it proposed? does it appropriately address bias, confounding, and measurement of endpoints?
what is external validity?
validity related to generalizing the study results outside the study setting: can the results be applied to other groups, patients, or systems?
define data maturation
when external changes occur within subjects which may explain in part or in total for effects discerned in the study rather than being caused by the study intervention
ex. a study reporting decrease in ED visits in a study of children with asthma may be because they outgrew childhood asthma rather than because of the treatment given
define repetitive testing
when changes in test scores occur not because of the intervention but because of repeated testing
define instrumentation
when study results are due to changes in instrument calibration or observer changes rather than an actual treatment effect
define regression
when subjects are chosen on the basis of extreme scores and therefore the study outcome cannot be accurately assessed
define differential selection
when subjects cannot be randomized into groups, particularly if groups are unequal in relevant variables before treatment intervention
example: one group is given an educational counsel of the treatment trial while the other group is given a mailed pamphlet. the first group will be more informed of the study and therefore the two groups are not equal with respect to relevant variables
define attrition
aka withdrawals or dropouts. problematic when subjects leave the study and cause the different groups in the trial to be significantly unequal. This can skew how beneficial/unbeneficial the treatment actually is
repetitive testing, instrumentation, regression, differential selection, and attrition are all examples of?
factors that affect a study’s internal validity
define study reliability (aka test, re-test reliability))
refers to the degree to which an instrument yields consistent results
—> if research is repeated and shows the same results each time then we can say the research design is reliable
what is IMRAD?
the most standard structuring for creating a study paper. it stands for:
Introduction- the why
Methods- how they did it and how they analyzed the results
Results
And
Discussion- what the results mean
what does it mean to develop a cognitive map?
the research paper describes the analytical process and guides the logic. the information provides a complete description of each internal-validity problem
