Exam 1 Flashcards
Define EBM
- Use of mathematical estimates of risk of benefit or harm, derived from research on samples to inform decision-making in clinical setting of diagnosis, investigation or mgmt. of individual patients.
Steps of EBM
- Ask answerable question (PICO – see flashcard) - Search for best evidence - Critical appraisal for validity and relevance - Integrate evidence, clinical expertise and patient values/preferences & apply - Evaluate results
Elements of an answerable question
- PICO - P: patient/problem/population - I: intervention - C: comparison intervention - O: outcomes
Types of clinical questions
- Background: general knowledge, typically for students, who/what/when/where etc - Foreground: seek specific knowledge for patient management (comprise ¾ PICO elements), for clinicians
What is the best medicine?
- Patient-centered
Qualities of best evidence in medicine?
- Current, valid and clinically relevant
Hierarchy of research studies by type and reliability
- Systematic review of RCTs (or meta-analyses) 2. RCTs 3. Prospective studies (typically cohort studies) 4. Retrospective studies (typically case-control) 5. Cross-sectional surveys 6. Case series 7. Case reports
Initial steps to evaluate a research paper
- Ask: Why study was done? What type of study was it? Was the study design appropriate?
Structure of research papers
- Mnemonic = A(IMRAD) - Abstract: summary - Intro: why research done - Method: how research structured - Result: findings - Analysis - Discussion
When evaluating a research paper, it is important to ask why the study was done and what hypothesis was tested? Where in the paper can this information be found?
- Intro - Hypothesis usually in intro, if not, in methods. Rarely is it found in the discussion (first paragraph).
Primary vs secondary studies
- Primary: experiments, observations, clinical trials, surveys, questionnaires 2. Secondary: reviews (systematic or non), economic analyses, decision analyses
Types of study questions. What study design is appropriate for each type?
- Therapy/intervention: RCT - Diagnosis: diagnostic validation study - Prognosis/prediction: cohort study - Harm/risk/etiology: RCT, cohort study, case-control study - Screening: ?
Define randomized controlled trial
- Subjects randomly assigned to one intervention group or another by random method. Groups should be similar, on average, except for the outcome.
Purpose of randomization
- Decreases selection bias while at the same time creating similar comparison groups.
Define concealed allocation vs blinding
- Concealed allocation: during RCT, randomization of subjects done by someone other than the investigator. - Blinding: prevents investigator or subject (single) or both (double) from knowing the group assignment (tx vs non-tx group).
Purpose of blinding
- Help avoid patients’ behaviors and ideas about treatment affecting results - Help avoid investigators inadvertently altering or changing the study results
Pros/cons of a RCT
- Pro: rigorous eval of a single variable, designed prospectively (less bias), seeks to confirm a null hypothesis, allow for meta-anlayses, minimize bias - Con: expensive, long-term (years sometimes), hidden bias (inadequate randomization, failing to randomize all eligible patients – investigator only offers entry to those who may benefit, failing to blind – see what you want to/expect to see)
Which studies tend to have less bias: retrospective or prospective?
- Prospective. We tend to see what we are looking for through our retrospectors.
Problems with randomization
- Can be unethical. Never randomize in harm study. - Impractical when # of subjects needed for statistical significance is huge
When is randomization inappropriate?
- Study involves prognosis of a disease (unethical) - Validity of a diagnostic / screening test - Investigating quality of care issues when criteria for success are not known yet
Which study designs are observational?
- Cohort studies - Case-control studies
What is a cohort study?
- Two or more groups selected based on exposure or no exposure to something in order to compare outcomes
What is a case-control study? What are case reports?
- Patients with certain conditions are matched with controls usually retrospectively for exposure to a disease-causing agent or circumstance. These studies are mostly concerned with harm or etiology. - Case reports: report of a medical history, sometimes a series of histories are reviewed/analyzed together. Weak statistically usually, but may give insight into rarities or unusual things.
What is a cross-sectional survey?
- Representative sample is interviewed, examined or evaluated about a specific question. Often information is retrospective. Can be used in studies looking to answer questions about etiology.