Evidence Based Medicine - Spring 2015
A study looking to reduce the incidence of DVT is found that 10% of treated patients experienced a DVT compared to 20% of control group patients. Calculate the following: ARR: RRR: NNT:
ARR = 20%-10% = 10% RRR= (1-(10/20))*100 = (1-0.5)*100 = 0.5*100 = 50% NNT= Since 10% of people benefit from treatment, you would need to treat 10 people in order for one person to benefit. Therefore NNT = 1/ARR = 1/0.1 = 10; or 100/10% = 10
What should be your approach to using medical literature to addressing diagnosis, treatment, harm, and prognosis? "the 5 As"?
Ask, Acquire, Appraise, Apply. Act 1. Ask: identify your problem 2. Ask: define a structured question 3. Acquire: find the best evidence (original primary study or evidence summary) 4. Appraise: how valid is the evidence? 5. Appraise: what are the results? 6. Apply: how should I apply the results to patient care? 7. Act: implement
Who coined the term "evidence-based medicine"? A. David Sacket B. Gordon Guyett C. Paul Glasziou D. Brian Haynes
B. Gordon Guyett
The steps in using the medical literature to provide optimal patient care are: A. Identify your problem; explore resources to find the best evidence; define a structured question; analyze the validity of the evidence; analyze what are the results; determine how the results should be applied to patient care. B. Identify your problem; define a structured question; find the best evidence; analyze the validity of the evidence; analyze what are the results; determine how the results should be applied to patient care. C. Identify your problem; define a structured question; find the best evidence; analyze what are the results; analyze the validity of the evidence; determine how the results should be applied to patient care. D. Define a structured question; identify your problem; find the best evidence; analyze what are the results; analyze the validity of the evidence; determine how the results should be applied to patient care.
B. Identify your problem; define a structured question; find the best evidence; analyze the validity of the evidence; analyze what are the results; determine how the results should be applied to patient care.
Identify the difference between a foreground/background question
BACKGROUND: "textbook" - can involve a single fact, e.g. cause of dz, etiology, drug dose; - list of attributes, e.g. attributes of syndrome FOREGROUND: "using current lit/research/studies" - targeted questions that provide evidentiary basis for specific clinical decisions, e.g. tx - best structured using framework of patient, intervention or exposure, possible comparison intervention, outcomes of interest (PICO) - e.g. why did HbA1C level for Dx of T2DM change?; can pt. on metformin take xyz?
Two fundamental principles of EBM are: A. 1. EBM uses a hierarchy of evidence to guide clinical decision making; and 2. Evidence alone is good enough to make a clinical decision. B. 1. EBM uses a hierarchy of evidence to guide clinical decision making; and 2. Expert opinion is the highest level of evidence. C. 1. EBM uses a hierarchy of evidence to guide clinical decision making; and 2. Evidence alone is never sufficient to make a clinical decision. D.1. EBM uses a hierarchy of evidence to guide clinical decision making; and 2. Evidence overrides patient preferences in making clinical decisions.
C. 1. EBM uses a hierarchy of evidence to guide clinical decision making; and 2. Evidence alone is never sufficient to make a clinical decision.
In Paul Glasziou's video, he talks about the four skills necessary to conduct EBM that are taught in most EBM curriculum. These skills are: A. Search for the best evidence; critically appraise the evidence; seek expert opinion; and combine individual clinical expertise and expert opinion to make a decision for the patient. B. Search for the best evidence; critically appraise the evidence; seek expert opinion; and combine individual clinical expertise with patient concerns. C. Formulate an answerable question; track down the best evidence; critically appraise the evidence; and combine individualized clinical expertise with patient concerns. D. Formulate an answerable question; track down the best evidence; critically appraise the evidence; combine the evidence with clinical expertise to make a decision for the patient.
C. Formulate an answerable question; track down the best evidence; critically appraise the evidence; and combine individualized clinical expertise with patient concerns.
- what is HARM?
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- what is a RANDOMIZED CONTROLLED TRIAL (RCT)?
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- what is the TREATMENT EFFECT?
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Analyze an article for potential strengths/weaknesses based on study design
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Apply calculations to patient care decisions
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Calculate NNT, likelihood ratios; odds ratios; sensitivity; specificity; PPV, NPV
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Demonstrate when it is more effective to search PubMed
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Discriminate between point of care resources based on their strengths/weaknesses
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Employ Information Mastery concepts to result in more targeted and effective searching for clinical questions
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Identify the appropriate statistical test based on the type of study design
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Recognize how confounders can effect the validity and reliability of the results
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what are levels of evidence / evidence rankings that are present in some tools?
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what is POINT ESTIMATE?
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what is the definition of Evidence Based Medicine (EBM)?
- "the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients" - "...the integration of best research evidence w/ clinical expertise and patient values" - skeptical attitude - favor knowledge from experiment
Identify the type of study design of a scholarly article
- 2 main types of study design: 1. observational: studies that do not involve any intervention or experiment; seeks to measure the freq. in which disease occur or collect descriptive data on possible causal factors → ecologic; cross-sectional; case report (unusual case, go back search lit for similar results) or case series (2+ cases);, case control (start w/ dz go back and look for exposure); cohort (start w/ exposure go back and look for dz) 2. analytical or experimental: studies that entail manipulation of the study factor (exposure) and randomization of subjects to treatment or control groups; attempts to specify in more detail the causes of a particular disease or the effect of an intervention → non-randomized control trail; RCT (double-blind, placebo controlled)
Identify key individuals and their contributions to the practice of EBM
- 900 AD: Al Razi, compiled methods, tested w/ control group - 1780: James Lind, British Navy, controlled trials for scurvy Tx; - 1840: Pierre Louis, Paris, blood letting "numerical method; - 1937/48: Bradford-Hill, principles of med. stats & MRC trial of streptomycin - 1938: John R. Paul & Alvan R. Feinstein at Yale, epidemiology observation and mathematical analysis of disease - 1967: Alvan Feinstein, "Clinical Judgement" - 1970s: David Sackett at McMaster SOM, new courses e.g. critical appraisal, clinical epidemiology & biostats; Archie ??? UK, "Effectiveness & Efficiency" - 1990: Drummond Rennie, editor at JAMA approached Sacket to update Readers Guides into "Rational Clinical Examination" − 1990-92: Gordon Guyatt, coined term Evidence Based Medicine, co-founder of Medical Reform Group, EBM at McMaster, JAMAs "Users' Guides" - 1993: Dave Sackett moves to Oxford; ward rounds w/ evidence cart
what is a CONFOUNDER?
- A factor that distorts the true relationship of the study variable of interest by virtue of also being related to the outcome of interest. Confounders are often unequally distributed among the groups being compared. Randomized studies are less likely to have their results distorted by confounders than are observational studies. - A factor that is associated with the outcome of interest and is differentially distributed in patients exposed and unexposed to the outcome of interest - e.g. gambling and lung CA link actually due to incr. smoking
- what is BIAS? - how can a study of an intervention (treatment) be biased?
- A systematic error in the design, conduct, or interpretation of a study that may cause a systematic deviation from the underlying truth (e.g., overestimation of a treatment effect because of failure to randomize) → intervention and control groups may be different at the start → intervention and control groups may, independent of the experimental treatment, become different as the study proceeds → intervention and control groups may differ, independent of treatment, at the end
what is the benefit of BLINDING?
- BLINDING clinicians to whether patients are receiving active or placebo therapy can eliminate the risk of important COINTERVENTIONS - blinding outcome assessors minimizes bias in the assessment of EVENT RATES
if the clinical question is CLINICAL EXAM, what is the suggested best type of study?
- Clinical Exam: prospective, blind comparison to gold standard
if the clinical question is COST, what is the suggested best type of study?
- Cost: economic analysis
if the clinical question is DIAGNOSIS, what is the suggested best type of study?
- Diagnosis: prospective, blind comparison to a gold standard
if the clinical question is ETIOLOGY/HARM, what is the suggested best type of study?
- Etiology/Harm: RCT > cohort > case control > case series
- when are observational studies compelling sources of evidence? - i.e. what are the criteria?
- If treatment effects are sufficiently large and consistent, carefully conducted observational studies may provide more compelling evidence than poorly conducted RCTs. - For example, observational studies have allowed extremely strong inferences about the efficacy of penicillin in pneumococcal pneumonia or that of hip replacement in patients with debilitating hip osteoarthritis. - Defining the extent to which clinicians should temper the strength of their inferences when only observational studies are available remains one of the important challenges in EBM
what is the n-of-1 RCT?
- In the n-of-1 randomized controlled trial (n-of-1 RCT), a patient and clinician are blind to whether that patient is receiving active or placebo medication - The patient makes quantitative ratings of troublesome symptoms during each period, and the n-of-1 RCT continues until both the patient and the clinician conclude that the patient is or is not obtaining benefit from the target intervention - N-of-1 RCTs can provide definitive evidence of treatment effectiveness in individual patients and may lead to long-term differences in treatment administration - Unfortunately, n-of-1 RCTs are restricted to chronic conditions with treatments that act and cease acting quickly and are subject to considerable logistic challenges. We must therefore usually rely on studies of other patients to make inferences regarding the patient before us.
what are LIKELIHOOD RATIOS (LR)? how are they calculated?
- LIKELIHOOD RATIO: is the likelihood that a given test result would be expected in a patient with the target disorder compared to likelihood that same result would be expected in a patient without the target disorder - LR is used to assess how good a diagnostic test is and to help select appropriate diagnostic tests or sequences of tests - advantage over predictive values b/c LRs do not change w/ prevalence: + LR+ is probability that an individual w/ dz has +test divided by prob. that indiv w/o dz has +test → LR+ = (test sensitivity)/(1-specificity); "ruling-in dz" → LRs <1 decrease prob of dz → LRs >1 increase probability of dz - LR- is probability that an individual w/ dz has -test divided by prob. that indiv w/o dz has -test → LR- = (1-sensitivity)/specificity; "ruling-out dz"
what is the Hierarchy of Strength of Evidence for Prevention and Treatment Decisions?
- N-of-1 randomized trial - Systematic reviews of randomized trials: combining written portion of research - Single randomized trial - Systematic review of observational studies addressing patient-important outcomes - Single observational study addressing patient-important outcomes - Physiologic studies (studies of blood pressure, cardiac output, exercise capacity, bone density, and so forth) - Unsystematic clinical observations
PICOtt
- P: - I: - C: - O: - t: - t:
Create an effective PICO question to guide search strategies
- Patient: - Intervention: - Comparison intervention: - Outcome of interest:
what two "studies" provide the weakest inferences about treatment effects?
- Physiologic studies and unsystematic clinical observations provide the weakest inferences about treatment effects.
if the clinical question is PREVENTION, what is the suggested best type of study?
- Prevention: RCT>cohort study > case control > case series
if the clinical question is PROGNOSIS, what is the suggested best type of study?
- Prognosis: cohort study > case control > case series
what is CONCEALMENT?
- Randomization is concealed if the person who is making the decision about enrolling a patient is unaware of whether the next patient enrolled will be entered in the intervention or control group (using techniques such as central randomization or sequentially numbered opaque, sealed envelopes). - If randomization is not concealed, patients with better prognoses may tend to be preferentially enrolled in the active intervention arm, resulting in exaggeration of the apparent benefit of intervention (or even falsely concluding that the intervention is efficacious). - See also Blind
what are the 4 categories of clinical information resources?
- Systems: - Synopses: - Summaries: - Studies:
if the clinical question is THERAPY, what is the suggested best type of study?
- Therapy: RCT>cohort > case control > case series
draw and label the PYRAMID OF SCIENTIFIC EVIDENCE
- as move ↑up pyramid → controls for comparison → less bias → stronger methodology
how do investigators studying the effect of potentially harmful exposures reduce placebo effects and bias in outcome assessment?
- blinding is impossible, so best defense against placebo effects and bias in outcome assessment is to choose ENDPOINTS, such as death, that are less subject to biases - minimizing loss to follow-up
what is a Point of Care (POC) tool?
- can use when have pt. in office
what is meant by "best available external clinical evidence" to support practice of EBM?
- clinically relevant research: → often from the basic sciences → especially from patient centered clinical research into accuracy and precision of diagnostic tests (incl. clinical exam) → power of prognostic markers → efficacy and safety of therapeutic, rehabilitative, and preventative regimens - external clinical evidence: both invalidates previously accepted diagnostic tests and treatments and replaces them w/ new ones that are more powerful, accurate, efficacious, safer
what is the structure for studies of differential diagnosis?
- collect a group of patients w/ similar presentation, conduct an extensive battery of tests, follow patients forward
*CASE CONTROL STUDY: - definition: - synonyms: - advantages: - disadvantages: - examples:
- definition: *compares patients who have dz or outcome of interest (cases) w/ pts who do not have dz or outcome (controls) and looks back retrospectively to compare how frequently the exposure to a risk factor is present in each group to determine the relationship btw risk factor and dz; observational b/c no intervention attempted, no attempt to alter course of dz; studies to ESTIMATE ODDS, not prove causation; care must be taken to avoid confounding; cases and controls should also not be "OVER-MATCHED" - synonyms: RETROSPECTIVE STUDIES; CASE-REFERENT STUDIES; - advantages: good for studying *rare conditions or dz; *less time needed to conduct b/c condition/dz already occurred; lets you simultaneously look at multiple risk factors; useful as initial studies to *establish an assoc.; can answer questions that could not be answered through other study designs - disadvantages: retrospective studies have more problems w/ data quality b/c they *rely on memory and people w/ a condition will be more motivated to recall risk factors (RECALL BIAS); not good for evaluating diagnostic tests b/c it's already clear that cases have condition and controls do not; *can be difficult to find a suitable control group; *confounders; - examples: SSRIs and risk of persistent PH in newborn; autoimmune and chronic inflammatory disorder and risk of non-Hodgkin lymphoma; risk of acute MI w/ current or former smoking, exposure to secondhand smoke; risk of lung CA w/ history of smoke exposure;
SYSTEMATIC REVIEW - definition: - advantages: - disadvantages: - examples:
- definition: *document written by panel that provides comprehensive review of all relevant studies on a *particular clinical or health-related topic/question; created after *reviewing and combining all info from both published and unpublished studies (focusing on clinical trials of similar treatments) and then *summarizing findings; studies may have varying designs but should be studying same outcome; - advantages: exhaustive review of current literature and other sources (unpublished studies, ongoing research); less costly to review prior studies than to create a new study; less time required than conducting new study; results can be generalized and extrapolated into gen. pop'n more broadly than individ. studies; more reliable and accurate than indiv. studies; considered an evidence-based resource; - disadvantages: v. time consuming; may not be easy to combine studies; *publication bias - examples: hawthorn extract in CHF
CASE REPORT STUDY: - definition: - advantages: - disadvantages: - examples:
- definition: an article that describes and interprets an *individual case (w/ 2-3 of people), often written in form of a detailed story; case reports often describe: unique cases that cannot be explained by known diseases or syndromes, cases that show an important variation of a disease or condition, cases that show unexpected events that may yield new or useful information; cases in which one patient has two or more unexpected diseases or disorders; The patient should be described in detail, allowing others to identify patients with similar characteristics. Case reports should include carefully recorded, unbiased observations. Case reports should explore and infer, not confirm, deduce, or prove. They cannot demonstrate causality or argue for the adoption of a new treatment approach. Case reports are considered the lowest level of evidence, but they are also the first line of evidence, because they are where new issues and ideas emerge. This is why they form the base of the evidence pyramid. A good case report will be clear about the importance of the observation being reported. If multiple case reports show something similar, the next step might be a case-control study to determine if there is a relationship between the relevant variables. - advantages: *can help ID new trends or diseases; *prelim. study; can help detect new drug SEs and potential uses (adverse or beneficial); educational - a way of sharing lessons learned; indentifies rare manifestations of a disease - disadvantages: *no control group; *no comparison; cases may not be generalizable; not based on systematic studies; causes or associations may have other explanations; can be seen as emphasizing the bizarre or focusing on misleading elements - examples: Kaposi's Sarcoma in homosexual men w/ HIV/AIDS; SARS Dx w/ chest CT
*COHORT STUDY: - definition: - advantages: - disadvantages: - examples: - 2 types:
- definition: one or more samples (COHORTS) followed *prospectively and subsequent status evaluations w/ respect to dz or outcome are conducted to *determine which initial participants exposure characteristics (risk factors) are assoc. w/ it; as study conducted, outcome in each cohort measured and relationships w/ specific characteristics determined; cohorts need to be chosen from separate, but similar, populations; cohort studies start w/ exposure and look for development of dz/outcome of interest - advantages: subjects in cohorts can be matched, which limits the influence of confounding variables; standardization of criteria/outcome is possible; easier and cheaper than a RCT; - disadvantages: cohorts can be difficult to identify due to confounding variables; no randomization, which means imbalances in pt. charac. could exist; blinding/masking is difficult; outcome of interest could take time to occur; - examples: effect of working for pay on adolescent tobacco use; outcomes of care by hospitalists, general internists, and family physicians; effectiveness of influenza vaccine in elderly; HRT & heart dz risk; - 2 types: 1. PROSPECTIVE cohort study: participants chosen on basis of exposure; followed over time until dz occurs 2. RETROSPECTIVE cohort study: participants chosen on basis of exposure; assessed for dz once enter study; some participants may already have dz;
RANDOMIZED CONTROLLED TRIAL - definition: - advantages: - disadvantages: - examples:
- definition: randomly assigns participants into an experimental or control group, only expected difference is outcome variable being studied; should be a study of 1 pop'n only; *variables being studied should be only ones btwn two groups - advantages: good randomization *will "wash out" any pop'n bias; easier to blind/mask than obs. studies; results can be analyzed w/ well-known stats tools; pop'ns of participating individuals are clearly identified; *control over exposure; *best for proving efficacy; - disadvantages: *expensive in terms of time & $; volunteer biases, pop'n that participates may not be rep. of whole; does not reveal causation; loss to f/u attributed to treatment; *ethical considerations; - examples: raloxifene ↓fracture risk in postmenopausal women; multimedia ed. resources ↑asthma control in children; use of bed-nets ↓malaria, anemia; zinc & duration of common cold, no diff
Which of the following are necessary for optimal evidence-based practice? A. Effective searching skills B. Effective critical appraisal skills C. In-depth background knowledge D. All of the above
D. All of the above
There are areas of EBM that have been neglected where there is limited information available to providers. One such area is: A. Evidence based physical examination testing. B. Evidence based population based healthcare interventions. C. Evidence based safety and quality improvement interventions. D. Evidence based monitoring/screening.
D. Evidence based monitoring/screening.
CROSS SECTIONAL STUDY : - definition: - advantages: - disadvantages: - examples:
- definition: representative sample of participants is recruited and then interviewed, examined or otherwise studied to gain answers to a specific clinical question; data are collected at a single time point; surveys or cross-sectional studies can be used to answer questions about a sample of a population - advantages: standardized data collection tool; able to focus data collection in specific locations or specific groups of persons; may make comparisons among study participants; relatively quick to do-doesn't require a long-term time commitment; may be repeated to get data on trends - disadvantages: may be biased by lack of participation (often will need to compare those who chose to participate vs. those who didn't to see how they may differ); reflects prevalent, not incident cases (can measure prevalent cases, but b/c not followed over time cannot assess new cases) - examples: national census; community survey; survey of particular group of persons (e.g. occupational group, school children); behavioral risk factor surveillance system (BRFSS)
PRACTICE GUIDELINES / EVIDENCE-BASED GUIDELINES / CLINICAL GUIDELINES - definition: - advantages: - disadvantages: - examples:
- definition: statement produced by a panel of experts to outline current best practice to inform health care professionals and patients in making clinical decisions; statement produced after extensive review of lit. and typically created by professional assoc., gov't ag., and/or public or private organizations; good guidelines clearly define topic, appraise and summarize best evidence regarding prevention, diagnosis, prognosis, therapy, harm, cost-effectiveness, identify decision points where info should be integrated w/ clinical experience and pt. wishes; should be reviewed frequently and updated as necessary; panel should be composed of a variety of experts w/ assorted affiliations - advantages: created by panels of experts; based on prof. published lit; practical guidelines for clinicians; considered an evidence-based resource; - disadvantages: slow to change or be updated; not always available, esp. for controversial topics; expensive and time-consuming to produce; recommendations might be affected by the type of organization creating the guideline; - examples: treatment of pressure ulcers;
META-ANALYSIS - definition: - advantages: - disadvantages: - examples:
- definition: subset of systematic reviews; a *method for systematically combining pertinent qualitative and *quantitative study data from several selected studies to develop a single conclusion that has *greater statistical power, due to ↑number of subjects; ↑diversity among subjects, or accumulated effects and results; *math - advantages: greater stat power; confirmatory data analysis; greater ability to extrapolate to gen. pop'n affected; considered an evidence-based resource; - disadvantages: difficult and time consuming to identify appropriate studies; not all studies adequate data for inclusion and analysis; requires advanced statistical techniques; heterogeneity of study pop'ns; *publication bias - examples: prevalence and incidence of CHD signif ↑ in periodontitis; CV risk factors for VTE;
what is the structure of randomized trials?
- eligible patients → randomization → → follow forward in time to determine whether they have outcome of interest
- what is a PLACEBO?
- identical-appearing but biologically inert treatments given to control-group patients
- contrast RANDOM ERROR with SYSTEMATIC ERROR (BIAS)
- in contrast to random error, bias leads to systematic deviations (i.e. the error has direction) from the underlying truth - in studies of treatment or harm, bias leads to either an underestimate or an overestimate of the underlying benefit or harm
- what is SYSTEMATIC ERROR? - what are two synonyms for SYSTEMATIC ERROR?
- introduced by studies flawed in their design or conduct - BIAS: - LIMITATION IN VALIDITY:
what are the 2 main types of STUDY DESIGN?
- observational: studies that do not involve any intervention or experiment; seeks to measure freq. in which diseases occur or collect descriptive data on possible causal factors: ecological, cross-sectional, case report or case series, case control, cohort - analytical or experimental: studies that entail manipulation of the study factor (exposure) and randomization of subjects to treatment or control groups; attempts to specify in more detail the causes of a particular dz or the effect of an intervention
- what is an OUTCOME? - what is the TARGET OUTCOME or TARGET EVENT?
- outcome: 1. Occurrence of a disease 2. The target variable of interest. The variable that is hypothesized to depend on or be caused by another variable, the independent variable. Treatment target or endpoint. - target outcome or target event: the adverse event that is the focus of a study
what is the "gold standard" for judging whether a treatment does more good than harm?
- randomized trial - systematic review of randomized trials: look at the written portion of studies with similar methodlogy
what are the data sources for EBM?
- randomized trials - meta-analyses - cross sectional studies of patients suspected of harboring the relevant disorder - follow-up studies for prognosis - basic sciences e.g. genetics, immunology
- what is RANDOM ERROR? - what is a synonym for RANDOM ERROR?
- results subject to play of chance - CHANCE: because of chance, no matter how powerful and well designed our experiment, we will never be sure of the true treatment effect
for each of the following, identify when and how to use each search terms: limits:
- search terms: synonyms, full words for acronyms - limits: age, language
what are the 4 selection criteria for choosing or evaluating resources?
- soundness of evidence-based approach: - comprehensiveness and specificity: - ease of use: - availability:
what are the characteristics of the ANALYTICAL or EXPERIMENTAL STUDY?
- studies that entail manipulation of the study factor (exposure) and randomization of subjects to treatment or control groups. Attempts to specify in more detail the causes of a particular disease or the effect of an intervention o Non-randomized control trial o RCT (double-blind, placebo controlled)
- what is VALIDITY?
- technical term that relates the magnitude of bias
what is INCIDENCE?
- the number of new cases of a disease per year
what is PREVALENCE?
- the overall proportion of the population who suffer from the disease
what are some factors that can lead clinicians astray as they try to interpret results of conventional open trials of therapy, and personal clinical observations?
- they include: -- natural history -- placebo effects -- patient and health worker expectations -- patient's desire to please
Identify the highest quality of study to answer a clinical question
- whether for issues of therapy or harm, the strength of inference from RCTs will almost invariably be >> strength of inference from observational studies
what is EXPOSURE?
1. Any trait, behavior, environmental factor, or other characteristic investigated as possible cause of disease a. May be a factor which leads to a protective effect against a disease 2. A condition to which patients are exposed (either a potentially harmful agent or a potentially beneficial one) that may have an impact on their health.
what are the 2 fundamental principles of EBM?
1. EBM posits a hierarchy of evidence to guide clinical decision making 2. evidence alone is never sufficient to make a clinical decision; decision makers must always trade off benefits and risks, inconvenience, and costs associated w/ alternative management strategies and, in doing so, consider patients' values and preferences
what are the 3 steps/questions in evaluating evidence?
1. are the results of the study valid? do these results represent an unbiased estimate of the truth or have they been influenced in some systematic fashion to lead to a false conclusion? 2. what are the results? consider the size and precision of the treatment effect (therapy); the evidence that helps us generate pretest probabilities and move to posttest probabilities according to test results (diagnosis); the size and precision of our estimate of a harmful effect (harm); and our best estimate of a patient's fate (prognosis) 3. how can I apply these results to patient care? first, can you generalize the results to your patient? second, what is the significance for your patient?
what are the 3 main reasons for the meteoric rise of evidence-based medicine in the 1990s?
1. catchy name, conveyed an intuitive message about the nature of the method 2. support of the McMaster Univ. SOM, and JAMA 3. social and cultural milieu of North America in the early 1990s was ripe for new methods; quantification practices, the use of statistics and epidemiology, introduction of computers and online digital databases, new clinical research methodology saturated the medical environment of the time
Identify concepts to be mastered over the semester
1. formulate an answerable question 2. track down the best evidence; journals w/ valid research articles 3. critically appraise the evidence; peer review 4. individualize, based on clinical expertise and patient concerns 5. evaluate our effectiveness - Cochrane database of systematic reviews - EBM research methods: randomized trials, cohort studies, etc.
Identify possible future directions for EBM
1. more evidence; better tools; 2. better search methods; easier, faster resources to look up info faster 3. better appraisal techniques; validation of positive impacts of practicing EM *4. better application methods; what do the results mean on average? what do they mean for this individual? how do I use in practice? → 1. chronic dz: single pt. trials; monitoring & adjustment → acute dz: predicting recovery → prevention: predicting future risk 5. evidence based monitoring, effectiveness of lab tests for monitoring - group based learning, e.g. journal clubs: 1. topics, new problems; 2. evidence, read appraise research paper for last week's problem/topic; 3. next actions, agree conclusions, organize changes in practice, follow up - who, what, when? - collaborations between practices: Improving Medical Practice by Assessing CurrenT Evidence (IMPACTE groups) w/ librarian and pharmacist support
what are the 3 components for framing clinical questions?
1. population: who are the relevant patients? 2. interventions or exposures (diagnostic tests, foods, drugs, surgical procedures, time, risk, factors); what management strategies are we interested in comparing? 3. outcome: what are the patient-relevant consequences of the exposure in which we are interested?
what are the 5 types of clinical questions?
1. therapy: determining the effect of interventions on patient-important outcomes (sx, fxn, morbidity, mortality, costs) 2. harm: ascertaining effects of potentially harmful agents 3. DDx: in pts. w/ clinical presentation, estab. freq. of underlying disorders 4. Dx: estab. power of a test to diff. btw w or w/o dz 5. prognosis: est. patient's future course
Definition of ADJUVANT
1: serving to aid or contribute 2: assisting in the prevention, amelioration, or cure of disease <adjuvant chemotherapy following surgery>
Two additional challenges in conducting evidence based medicine in regards to the literature are: A. Lack of training in how to take published results and individualize them to patient care and an overabundance of editorials and opinion papers published. B. Lack of training in how to take published results and individualize them to patient care; and lack of good systematic reviews. C. Peer reviewers are not properly trained in the peer review process leading to poor quality studies being published and lack of good systematic reviews. D. Peer reviewers are not properly trained in the peer review process leading to poor quality studies being published and only 1 in 200 articles are both valid and relevant.
D. Peer reviewers are not properly trained in the peer review process leading to poor quality studies being published and only 1 in 200 articles are both valid and relevant.
According to the article, "EBM: What it is and what it isn't", the practice of evidence based medicine means: A. Integrating individual clinical expertise with the best available external evidence...in the use of individual patients' predicaments, rights, and preferences. B. Integrating individual clinical expertise with the best expert opinion...in the use of individual patients' predicaments, rights, and preferences. C. Integrating best external evidence with expert opinions to provide high quality, cost effective healthcare. D. Integrating patient values with the best available external expert opinions to provide high quality, cost effective healthcare.
A. Integrating individual clinical expertise with the best available external evidence...in the use of individual patients' predicaments, rights, and preferences.
In the Hierarchy of Strength of Evidence for prevention and treatment decisions, the top 3 levels of evidence are: A. 1. N-of-1 randomized trial; 2. Systematic review of randomized trials; 3. Single randomized trial B. 1. Unsystematic Clinical Observations; 2. Systematic Review of Observational Studies; 3. Systematic Review of Randomized Trials C. 1. Single Randomized Trial; 2. Systematic Review of Observational Studies; 3. Single Observational Study D. 1. Single Randomized Trial; 2. Observational Studies; 3. Expert Opinion
A.1. N-of-1 randomized trial; 2. Systematic review of randomized trials; 3. Single randomized trial
Two of the challenges providers face in conducting evidence based medicine are: A. <5% of journals have studies that are valid and <5% of journals have studies that are relevant. B. 5-10% of journals have studies that are valid and 5-10% of journals have studies that are relevant. C. 10-15% of journals have studies that are valid and 10-15% of journals have studies that are relevant. D. 15-20% of journals have studies that are valid and 15-20% of journals have studies that are relevant.
A.<5% of journals have studies that are valid and <5% of journals have studies that are relevant.
how can you use Likelihood Ratios as Bedside Estimates without a pretest probability?
Likelihood Ratio → Approximate Change in Probability (%)* Values between 0 and 1 decrease the probability of disease 0.1 −45 0.2 −30 0.3 −25 0.4 −20 0.5 −15 1 0 Values greater than 1 increase the probability of disease 2 +15 3 +20 4 +25 5 +30 6 +35 7 8 +40 9 10 +45
NNT
NNT = 100/ %absolute risk reduction; or 1/ARR expressed as decimal value
what are the characteristics of the OBSERVATIONAL STUDY?
Observational: studies that do not involve any intervention or experiment. Seeks to measure the frequency in which diseases occur or collect descriptive data on possible causal factors. o Ecologic o Cross-Sectional o Case report or case series (start w/ one unique case, go to lit to see if reported elsewhere) o Case Control: start w/ disease go back and ask about exposure o Cohort Observational study designs can differ in a number of ways: • Number of observations made o Once or many times • Directionality of exposure/intervention o Start with disease and ask about exposure (*case control) o Start with exposure and evaluate for development of disease (*retrospective cohort) • Data collection methods o Data already collected o Collection of new data • Timing of data collection o When exposure/intervention happens or much later in time • Unit of observation o Groups vs individuals • Availability of subjects o Phone surveys o Need to recruit within a clinical environment
Create an effective PICO question to guide search strategies: A 65-year old man, smoker since age 13, has a non-fatal heart attack and has finally decided it is time to stop smoking. TV told him Zyban (bupropion) will help him quit. You normally prescribe bupropion as a stop-smoking aid but you are worried about the safety of bupropion after an MI.
P: 65 YO man with a history of smoking and MI I: Buproprion C: Placebo (or other stop-smoking aids) O: Cardiovascular morbidity or mortality
what is the structure for studies of prognosis?
identify patients in a particular group and follow over time to see if experience a target outcome
what is the structure for studies of diagnostic test properties?
patients in whom suspect dz called target condition → pts undergo new diagnostic test and a reference standard, gold standard, or criterion standard
what is the structure of observational cohort studies?
patients with and w/o exposures of interest followed forward to determine whether they experience outcome of interest
Identify challenges and limitations of practicing EBM
− access to the current best evidence & clinicaly relevant research - keeping abreast of all medical advances, requires reading 19 articles/day, 365 days/year - individual clinical expertise decides whether external evidence applies to indiv. patient + patient choice - EBM will be hijacked by purchasers and managers to cut costs of health care - keeping up with EBM happens least in primary care;
Analyze what areas of deficiency exist in understanding EBM and Information mastery concepts
− not happening everywhere, patchy in training around the world - a lot of poor research: is it valid? is it relevant?; need to read 200+ articles to find 1 valid; peer-reviewed, is that enough, not trained
what was the paradigm shift in the practice of medicine in the 1990s?
"A new paradigm for medical practice is emerging. Evidence-based medicine de-emphasizes intuition, unsystematic clinical experience, and pathophysiologic rationale as sufficient grounds for clinical decision making and stresses the examination of evidence from clinical research"