Clinical Studies Exam 1

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grey literature

Back 1

personal letters, thesis, dissertation...
unpublished material

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heterogeneity in statistics
why do you have to access this in meta analysis?

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heterogeneous- means there is variability across the studies due to more than just chance (can look at confidence intervals, study statistics and see if they are somewhat similar across studies)

make sure you account for differences across the studies, and while there is bound to be some heterogeneity, we want to make sure it is not too drastic.

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purpose of doing a meta analyses

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increase statistical power of smaller population trials by lumping a bunch of them together into one big population

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systematic way of answering a DI question (7)

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1) obtain demographics of person asking
2) get bg info
3) determine/categorize the ultimate question
4) strategy and search
5) analyze, evaluate, synthesis
6) formulate and provide response
7) deliver answer and follow up

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how would you conduct the search process when answering a DI question?

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start with tertiary literature and work up to primary literature.

make sure you confirm with other sources to minimize error.

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literature pyramid (and define sources)

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from tip to bottom

tertiary- general info, often gathered from more primary sources
secondary- indexing and abstracts for primary lit
primary- published articles in journals (the "source" of it all). the "cutting edge" (most up to date)

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4 examples of tertiary lit

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textbooks, other books, databases, review articles

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3 examples of secondary lit

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pubmed, IDIS, IPA

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4 examples of primary lit

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journal articles, editorials, letters to the editor, case reports

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hierarchy of evidence strength (from strongest to weakest) (9)

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systematic review/meta analyses
randomized controlled double blind studies
cohort studies
case control studies
case series
case reports
ideas, editorials, opinions
animal research
IVT research

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prospective

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data collected forward in time from start of study

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PICO (what is it used for, what does it stand for)

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used for formulating clinical questions and for database searching help

Patient
Intervention- what is currently being done (either nothing, or current therapy); what do you want to do to the patient
Comparison- what you want to compare the current therapy to
Outcome- what is relevant? what are you looking for?

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what items do you look at when screening a journal? (5)

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1) title- can be misleading though
2) does it follow CONSORT?
3) is the journal peer reviewed?
4) does journal require trials to be registered (IMPORTANT. unregistered trials are sketchy)
5) is the abstract structured or unstructured?

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what does CONSORT recommend for abstracts? (5)

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Descriptive stuff: Title, author, trial design, summary of methods
Results
Conclusion
Trial registration
Source of funding

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case report

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descriptive study on one individual. very detailed report usually written up when there is some new or unique happening

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case series (2)

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descriptive report on a small*** group of individuals with similar disease/treatments or with similar findings

can be retro or prospective

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what is evidence based practice?

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convergence of best evidence, patient values, and practitioner expertise

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format characteristic of case report/series

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spontaneous and anectodal

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advantages of case report/series (2)

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1) can alert FDA to unknown side effects, toxicity, efficacy of a drug
2) can help formulate new research questions

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disadvantages of case report/series (3)

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1) subject to bias
2) uncontrolled
3) unable to determine causality as it is only observational

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synonyms of cohort study (3)

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follow up study
longitudinal study
incidence study

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definition of cohort

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group of people who share similar characteristics

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structure of prospective cohort study

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take 2 "cohorts" (start with groups not exhibiting any of the desired observational outcome). divide into positive and negative exposure. outcomes are observed after period of years.

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retrospective cohort study

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positive/negative cohort was identified and enrolled from the past, and progress followed to present time (outcomes accessed at present, rather than future)

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advantage of cohort study

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can study relationship of outcome and exposure over time

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disadvantages of cohort study (4)

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1) subject to bias
2) unable to establish causality
3) long follow up periods can be costly
4) may need large sample size if outcome is rare

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case control study

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start by identifying if cohort did or did not (control) have the outcome. usually retrospective. follow backwards through time to evaluate how each group fared in terms of the outcome of interest. can also flip flop outcome and exposure (e.g. start with group that had exposure and one that did not-->follow backwards through time to ID outcomes)

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what is good to use case control studies for? elaborate

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adverse effects (ID cohort that had a specific adverse effect and those that did not-->follow through time to see how many from each group was taking drug of interest)

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advantages of case control

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efficient design for studying rare outcomes and disease (you can start with outcome and move backward)

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disadvantages of case control (4)

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again, establish relationship but no cause
difficult to ensure complete data due to retrospective nature (you're stuck with what you've got)
because of incomplete data, temporal relationship can be hard to ID
difficult to control for confounding/bias

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characteristics of experimental studies (4)

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1) treatments ASSIGNED by investigators (manipulation of independent variable)
2) has both dependent and independent variables
3) control of study conditions
4) randomization

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POE (and 3 examples)

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patient oriented evidence
things like...morbidity, mortality, quality of life

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DOE (and 3 examples)

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drug oriented evidence
things like how drug affects...pathology, etiology (origination of disease), alteration of disease process over time

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important things to consider when assessing causal associations (7)

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1) magnitude of association (correlation?)
2) how reproducible is it
3) how specific is the association
4) temporal sequence
5) dose response relationship (does the correlation change with dose?)
6) biologic plausability (make sure it isn't something completely stupid you are claiming)
7) coherence with common knowledge (does it mesh with what we already know)

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where are RCTs used mostly? for what purpose?

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clinical trials
really good for establishing causality evidence/correlation

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parallel RCT

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2 groups--> each get one treatment (control + drug, or whatever) for entire duration of study-->follow them through to the outcome

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crossover RCT

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the groups take both treatments with washout periods in between. patients act as their own control.

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disadvantages of parallel RCT (3)

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1) expensive
2) hard to recruit enough subjects (need more than crossover) if disease is rare
3) rare adverse effects difficult to detect (if limited to small populations)

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advantages of crossover RCT

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1) better control since patient is their own "control"
2) less costly than parallel since you don't need to divide up your population into strictly placebo groups

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disadvantages of crossover RCT (3)

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1) must control for carryover/sequence events from previous treatments
2) doubles time of participation for subject
3) may not be suitable for studying chronic diseases because they require constant medication

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N of 1 study

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study of an individual using clinical trial features using a randomized sequence of drug dosing

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when is it best to use N of 1 study? (6)

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1) when there is significant doubt about treatment efficacy (don't want to build up a whole trial to test a drug that might not work)
2) potential exists for harm or benefit
3) prolonged or expensive treatment is being considered (don't have to pay for trial drug; prolonged allows for time to study)
4) chronic disease
5) patient able to comply with keeping symptoms diary (e.g. not blind or has no arms)
6) relevant outcomes are measurable

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advantage/purpose of N of 1 study

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enables physician/pharmacist to study and individualize treatment for a specific patient (dose, dosage form, indication) to determine causality

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disadvantages of N of 1 study (3)

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-difficult to generalize to other patients
-could be too time consuming and costly for patient (if they are required to pay) (and investigator)
-more difficult to interpret and apply statistical tests (n=1)

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when does randomization occur in N of 1 study

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when determining which drug to give in each trial period so there are no confounding factors like time each drug was administered

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systematic definition

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pertaining to a single clinical question

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defining characteristics of a nonsystematic review (5) (unpublished lit? blinding? evaluations? type of clinical question?)

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-broadly defined clinical question -no real literature search strat
-no evaluations really
-does not include unpublished literature
-no blinding of reviewers

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systematic qualitative review: defining characteristics (6)

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clearly defined and focused clinical question
-predefined inclusion/exclusion criteria (for articles?)
-can include unpublished literature
-blinding of reviewers
-rigorous and objective analysis
-results are not statistically evaluated

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systematic quantitative review: defining characteristics

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same as qualitative except includes statistical analysis or re-analysis of all the data (qualitative will only analyze based on observations from the studies)

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strengths of narrative (nonsystematic) reviews (3)

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-useful for learning (overview of unfamiliar topic)
-can help clinician to understand better/evaluate issues associated with disease/condition/therapy
-good source of citations of clinical trials and other reports

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shortcomings of narrative reviews (3)

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-considered tertiary literature
-ergo, may not be current
-can present reviewers bias on funding sources, specialties, clinical judgments

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strengths of systemic reviews (4)

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-focused on specific question or issue
-utilize defined criteria for searching and selecting literature (like inclusion/exclusion criteria for patients in RCT)
-can help resolve uncertainty in studies with conflicting results
-methodology for combining data may offset low statistical power (probability that test will not produce a false negative)
null hypothesis is usually the default "setting"- e.g. drug will not work

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weaknesses of systemic reviews (3)

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-cannot compensate for poor validity in studies analyzed
-subject to publication bias
-meta analysis is influenced by variance between and within studies

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how to assess validity of a study (3 ways)

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1) is the data accurate and precise?
2) Conclusions sound?
3) To what extent does this trial affect people who were not subjects in the study?

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internal validity

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how well was the study designed (how seriously can we take the conclusion)

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external validity

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how well can we extrapolate this data to patients not in the clinical trial

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what does it mean if internal validity is strong?

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the conclusion is very sound

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what does it mean if external validity is strong?

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you can extrapolate with confidence

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primary endpoint

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main result measured at the end of a study to see if treatment worked