BIOSTATS FML #2
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What is meta-analysis?
Combine literature about a topic to arrive at a single summary estimate
Why is meta analysis used?
- Confirm results
- Reconcile outcomes
- Realize and quantify undetected treatment effect
Steps in a meta analysis?
- Clearly specify all databases
- Identify all studies on the topic even unpublished data
- Systematic and transparent process to select studies for inclusion
- Use structured format to extract outcomes from study
- Combine the data
- Have explicit inclusion and exclusion criteria
What are the strengths of the meta analysis?
- Quality of methods
- Finding relationships across studies
- Imposes process of summing up research findings
T/F The quality of the methods is central to the quality of the results?
Limitations of meta anaylsis?
- If study is comparable based on individual opinion
- Includes some less than optimal studies
- Selection and publication bias
When to use a meta analysis?
- Studies lack substantial power
- Available results support different conclusions
- More precise estimate of treatment effect
T/F - Do all hypothesis refer to the population?
What does a parameter describe?
- Describes the characteristic of a population.
- Always in GREEK letters
What does a statistic describe?
- A chracteristic of the sample
- Always in ROMAN letters
What are the 2 statistical methods?
What is descriptive statistics?
Collecting, presenting, describing data using formulas, graphs, surveys
What is inferential statistics?
- Draw conclusions/make decisions about a population based on sample data only
- Hypothesis testing
What are the 4 levels of measurement?
- Nominal - unordered categories no true meaning of value
- Ordinal - rank ordered categories
- Interval - no true zero point
- Ratio - true zero point
What is a cohort study?
- Follow up
- Can be prospective or retrospective design
- Nonrandomized study grps are assigned
- Observational - researchers only observe
- Longitudinal - takes a long time to do
What are the 6 advantages of cohort study?
- Study rare diseases
- Outcome timeline
- Avoid recall and survival biases
- Assess multiple outcomes
- Measure exposure over time
- Measure outcome incidence
What are the disadvantages to cohort study?
- Selection bias
- Large sample for rare/slow disease
- Accurate records
- Loss to follow up
- Exposure status changes over time
What is prospective cohort study?
Exposed at beginning of study follow up in the future
What is retrospective cohort study?
Exposed in the past (historical) outcome assessed as historical records
What are equal measurements?
- Equal testing and examining in the same way
- Same diagnostic tests
What are homogeneous grps?
How to calculate relative risk? pg.18
- Relative risk = (a/a+c)/(b/b+d)
- >1 = no association
- <1 = exposed ppl have less risk
- =1 = equal risk
checklist of what needs to be included in cohort studies. ex. intro methods...
What is case control?
- Determine the association between risk factors and outcome of interest
- Retrospective data collection by choosing subjects in present time already with outcome and checking for risk factors
What are the advantages to case-control studies?
- Study rare diseases/ long development type things
- Easy to perform and collect data
- Hypothesis generation
What are the disadvantages to case control studies?
- Correlation no causation
- No time link of outcome and risk
- Can't calculate outcome incidence
- Inefficient for rare risk factors
- Hard to select representatives for cases and controls
What bias occurs in case-control studies?
- Design bias
- Recall bias - based off of memory
- Researcher bias
What is a randomized controll trial?
- Random assignment of participants into experimental grp and control grp
- Only difference between the grps is the outcome variable studied
T/F Are all clinical trials interrelated?
What is the format for how information for a trial should be?
IMRAD - intro, methods, results, and discussion
What are the advantages of parallel trials?
- Robust for most conditions
- Large subjects
- Fits most experimental situations
What are the disadvantages of parallel trials?
- Only one treatment
- Need to match subjects for
What are the 4 types of parallel tests?
- Simple parallel
- 3 grp parallel
- 2 part parallel
- Multiple dose parallel
What are characteristics of crossover trials compared to parallel trials?
- Each subject gets all treatments
- Subject is its own control
- Less data varability
- Less subjects
- More sensitivity
- Less robust
What are the 3 order effects?
- Carry-over = drug effect lasts from treatment period to treatment period, reduced with washout period
- Period = change in pt condition between treatment
What is an N-of-1 trial?
- Controlled cross-over study of 1 person comparing their treatment effects to their placebo effects to see if effective
- Can't apply results to population only to pt
How many phases in a random control trial?
What happens in phase 1?
- Healthy human volunteers
- Short duration
- Assess PK, toxicity, pharm effects
- Monitor ADR
What happens in phase 2?
- Safe and effective
- Have disease condion of interest
What happends in phase 3?
- Safe and effective
- Large grp 1000's
- Have disesase and comorbid conditions
What happens in phase 4?
- Post market studies
- Use, effects, and safety in real world conditions
What are cross sectional studies?
- Observational study
- Conducted at single or more points in time
- Simultaneous selecton, assignment, and asessment of subject
What are the 2 types of cross sectional studies?
- Descriptive - have or no have, point prevalence (1 point in time) or period prevalence
- Analytical - compare
What are case reports?
- Describe observations
- More knowledge of treatment/condition
- Safer treatment practices
- Start new research
What are case series?
- Grp of single cases in one report
- Subjects have common characteristic
- Quick and cheap way to report info
- Shows trends
- Start new research
- Report epidemics
- Evaluate efficacy
What are the limitations of case series?
- Can't determine causal inferences
- No control grps
- No circumstantial evidence
- Fail to compensate for influences of external forces
What are the 3 types of review articles?
- Systematic (qualitative)
- Meta-analysis (quantitative)
What is a narrative review article?
- Editorial type - short and narrow focused
- Commentary type - biased, express a particular opinion
- Narrative Overview - author's summary of literature (bias)
What is systemic articles better than (narrative articles)?
- Focused questions (broad)
- Comprehensive lit search (not specified)
- Criterion based selection (not specified)
- Rigorous appraisal (variable)
- Quantitative (qualitative)
- EBM inferences (sometimes)
Why is meta analysis good?
- Combine independent results of trials using statistical analysis to draw conclusions about therapeutic effectiveness or plan new studies
- Small samples used in original trials
- Large trial too expensive to perform
- Solves disagreements on magnitude or direction of effect
List the tests in order that provide the most to least evidence?
- Case series
- Case reports
What would you like to do?
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