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Questions and Answers
What does a relative risk (RR) of 1 indicate?
What is indicated by an odds ratio (OR) greater than 1?
What is a characteristic of selection bias?
Why can relative risk not be performed with a case-control study?
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What does internal validity refer to?
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What is the relationship between rate ratios and risk ratios for rare diseases?
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How can confounding variables affect research?
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What does a P value greater than 0.005 indicate?
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What is a primary advantage of conducting a systematic literature review compared to individual studies?
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Which of the following is NOT a prerequisite for conducting a meta-analysis?
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Which statistical method is suitable for both binary and continuous data in meta-analysis?
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In which scenarios should the Mantel-Haenszel method be used?
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What is the fundamental assumption of the fixed effects model in meta-analysis?
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Which of the following statements about the random effects model in meta-analysis is true?
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Under which condition would Peto's method be appropriate in a meta-analysis?
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What does testing the fixed effects assumption with a test of homogeneity help determine?
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What does sensitivity measure in diagnostic accuracy studies?
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Which statement best describes specificity in diagnostic tests?
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Why is the Positive Predictive Value (PPV) important in diagnostic tests?
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What does a high sensitivity test imply?
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In health economic evaluations, what is the primary goal?
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Which of the following factors does NOT affect Positive Predictive Value (PPV)?
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What is a diagnostic accuracy study primarily concerned with?
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Which term describes the ability of a test to correctly identify individuals without a condition?
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In the Markov model, which health state is considered an absorbing state?
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Which transition probability from the sick state is highest?
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Which statement best describes the relationship between rates and probabilities in health modeling?
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How should probabilities be transformed to adjust or convert them into rates?
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What is meant by the term 'deterministic decision analysis' (DDA)?
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What is primarily determined by the physician-patient decision process in healthcare?
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Which type of study design is ranked highest in the hierarchy of evidence development?
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In the context of health economic modeling, what is the primary purpose of a meta-analysis?
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What defines whether a drug is considered too expensive?
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Which of the following statements about the Markov model is correct?
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When assessing the cost-effectiveness of a drug, which aspect is typically uncertain?
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What is the first step in developing a value dossier for pharmaceutical assessment?
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What does the memoryless property in a Markov model imply?
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Study Notes
Systematic Review
- Larger sample size than individual studies allows for subgroup analysis.
- Results of systematic reviews are more accurate than individual studies due to larger sample size.
- Meta-analysis is a specific type of systematic review that uses quantitative assessment of outcome parameters.
Meta-Analysis
- Not all systematic reviews include a meta-analysis.
- Requires studies to include (approximately) the same intervention, patient population, and outcome measures.
- Studies must meet acceptable methodological quality standards.
- Three statistical methods for meta-analysis: Inverse Variance-weighted method, Mantel-Haenszel, and Peto.
Inverse Variance-weighted Method (IV)
- Suitable for all outcome measures (OR, RR, RD, MD, etc.).
- Applicable for both binary and continuous data.
Mantel-Haenszel (MH)
- Used when data is sparse (low event rates and small trials).
- Only suitable for binary outcomes.
Peto
- Suitable for odds ratios and when the event of interest is rare.
- Not suitable for large treatment effects
Fixed Effects Model
- Assumes a fixed treatment effect (same value in each study).
- Differences in results are attributed to chance.
- Assumes studies estimate the same effect size.
- Requires testing the fixed effects assumption with a test of homogeneity.
Random Effects Model
- Assumes effect sizes may differ.
- Differences in results are not purely due to chance.
- Incorporates more uncertainty.
- DerSimonian and Laird method is used to incorporate heterogeneity.
- Confidence intervals in random effects models are wider than fixed effects models.
Relative Risk (RR)
- Two types: risk ratio and rate ratio. = 1: No increased risk, no association.
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1: Increased risk, positive association.
- < 1: Decreased risk, negative association.
- Reported along with a p-value.
- Cannot be performed with case-control studies.
Odds Ratio (OR)
- Used in both cohort and case-control studies. = 1: Exposure not associated with disease.
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1: Exposure positively associated with disease.
- <1: Exposure negatively associated with disease.
- Rate Ratios and Risk Ratios are similar for rare diseases.
Bias
- Systematic error that leads to incorrect conclusions about the true effect of an exposure on an outcome.
- Undermines the internal validity of research.
- Selection bias: Results from differences in study groups in important aspects (sampling, attrition, volunteer).
- Information Bias: Misclassification or inaccurate reporting of information (reporting, recall, observer).
Confounding Variable
- Real but misleading associations.
- Related to both the cause and effect of the study.
- Stratification can be used to reduce the impact of confounding variables.
Internal and External Validity
- Internal validity: Whether the conclusions about the cause and effect relationship in a study are valid.
- External Validity: The extent to which study results can be generalized to another context.
Sensitivity and Specificity
- Measures of the accuracy of a diagnostic test.
- Sensitivity: Ability of a test to correctly identify individuals with the condition.
- Specificity: Ability of a test to correctly identify individuals without the condition.
- Positive Predictive Value (PPV): Likelihood that someone with a positive test result has the condition.
Positive Predictive Value (PPV)
- Probability someone with a positive test result actually has condition.
- High sensitivity screening tests (low false negatives).
- High specificity confirmatory tests (low false positives).
Health Economic Evaluations
- Comparative analysis of two or more alternative investment possibilities (interventions, strategies, policies).
- Goal is to identify, measure, value, and compare costs and consequences of alternatives.
Types of Healthcare Decisions
- Market Approval Decisions (EU Regulation)
- Market Access and Pricing Decisions (Companies)
- Reimbursement of New Pharmaceuticals and Medical Devices (Ministers of Health, National Insurance)
- Physician Decisions about Medical Treatments (Physician/Patient)
Hierarchy of Evidence Development
- IV: Expert Opinions
- III: Non-experimental Studies
- IIb: Quasi-experimental Studies
- IIa: Controlled Studies without Randomization
- Ib: Well-Performed RCTs
- Ia: Systematic Reviews of Well-Performed RCTs
Market Authorization
- Process of evaluating the safety and efficacy of drugs, etc.
Development of a Value Dossier
- Collecting and synthesizing evidence for the cost-effectiveness of a treatment.
Requesting Reimbursement
- Considerations include: budget, affordability, pricing, access, and return on investment.
Markov Model
- Mathematical model that simulates the progression of individuals or systems through various states over time.
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Key Components:
- Mutually Exclusive: Only one state at a time.
- Cycle: Individuals move between states at each time period.
- Transition Probabilities: Likelihood of moving from one state to another.
- Memoryless Property: Transition probabilities depend only on the current state.
- Example: A simple chronic disease can be modeled with health states (Healthy, Sick, Dead), transition probabilities (moving between states), cycle length, and costs/utilities for each state.
Deterministic Decision Analysis (DDA)
- Uses mean values for each input parameter, assuming exact values are known.
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Description
This quiz covers the essential concepts of systematic reviews and meta-analyses, focusing on different methods used in the analysis. You will learn about the importance of larger sample sizes, subgroup analysis, and the specific statistical methods for conducting a meta-analysis. Understand the distinctions and applications of the Inverse Variance-weighted method, Mantel-Haenszel, and Peto methods.
