Critical Appraisal of Epidemiological Studies and Clinical Trials

Introduction; 1. The important of causal relationships in medicine and health care: What is causation?; A direct test of causation; Methods of counting events; Summary; Self-test questions; 2. Study design which can demonstrate and test causation: Relationship of study design to the definition of causation; A classification of comparative studies; Classification by groups of people compared; Classification by time relationships; More complex designs; Characteristics of the different study designs: intervention trials; Observational cohort studies; Case-control studies; Cross-sectional surveys; Summary of comparisons; Summary; Self test questions; 3. The results obtained from studies of causation: Cohort and intervention studies; Relative risk and relative odds; Risk difference (attributable risk); preventive factors, and application to intervention studies-number needed to treat; person-time as the denomator of rates; More than one causal agent; Case-control studies; Use of the odds ratio; Different sampling schemes in case-control studies: why a cause can also be a control; Surveys; general applicability of these analytical approaches; Summary; Self test questions; 4. Selection of subjects for study: Target, source eligible, and participant populations; the distinction between internal and external validity; selection bias and its effects; Methods of reducing selection problems; Selection of subjects for comparative studies; Selection of the comparison studies; Selection of subjects in randomized intervention studies; Selection of subjects for a cohort study; Selection of subjects for a case-control study; Choice of the control group in case control studies; Assessment of selection issues in a completed study; Summary; Self test questions; 5. Error and bias in observations: Sources of error and bias; Practical issues in reducing bias and error; Examples of bias; Assessment of bias and error; Assessment of the consistency of information; Effects of misclassification on study results; Summary; Self test questions; 6. Confounding: Confounding - definition and non-mathematical examples; confounding in cohort and intervention studies; Confounding in case-control studies; Methods for the control of confounding; Control of confounding; restriction; Randomization; Stratification; Matching; Multivariate methods; Application of the definition of confounding to study design; Application of the definition of confounding to analysis; Summary; Self test questions; 7. Chance Variation: The concept of significance; Simple statistical tests for a two-by-two table; The Mantel-Haenszel test. The concept of precision; confidence limits; Statistical power and the size of the study; repeated testing in trials - stopping rules and data monitoring groups; Ordered exposure variables and tests of trend; Assumptions in stratification; interaction; Statistical tests in matched analysis; Statistical tests in multivariate analysis; Issues in the interpretation of results; Summary; Self test questions; 8. Combining results from several studies: meta-analysis: The process of meta-analysis; Publication bias; Finding and selecting studies for inclusion; Analyses based on original data, or on published results; Limitations of meta-analysis; Exploring differences between studies; Statistical methods in meta-analysis; the Cochrane collaboration; Summary; Self test questions; 9. The Diagnosis of causation: What evidence do we have? Description of the evidence; Internal validity - consideration of non-causal explanations; Internal validity - consideration of positive features of causation; External validity - generalization of the results; Comparison of the results with other evidence; Assessing causal relationships in making decisions; Further application of these concepts; Application of the scheme in designing a study; The application of critical appraisal to health care decisions - evidence based medicine; Summary; Critical appraisal of published work - introduction; 10. Critical appraisal of a randomized clinical trial; 11. Critical appraisal of a randomized trial of a preventive agent; 12. Critical appraisal of a prospective cohort study; 13. Critical appraisal of a restrospective cohort study; 14. Critical appraisal of a matched case-control study; 15. Critical appraisal of a large, population based, case-control study; Answers to self test questions; Appendices; Appendix 1: Statistical analysis methods: formulae and worked examples; Appendix 2: Lifetable methods: List of contents; Appendix 3: Statistical Tables: list of tables; References; Index