Causation Assessment and Methodology

Transcription

1 Causation Assessment and Methodology Kurt T. Hegmann, MD, MPH University of Utah Content Attestation I, Kurt Hegmann, MD hereby declare that the content for this activity, including any presentation of therapeutic options, is well balanced, unbiased, and to the extent possible, evidence-based. Conflict of Interest Disclosure I have no financial relationships with commercial entities producing, marketing, re-selling, or distributing health care goods or services consumed by, or used on, patients relevant to the content I am planning, developing, presenting, or evaluating.

2 Conflict of Interest Disclosure Chair, ACOEM Evidence-Based Practice Committee and Editor-in-Chief Teaching and Research Grants (CDC/NIOSH); Utah Labor Commission Take care of patients (primary to tertiary) Consultations >100 businesses and unions 4 Steps for Concluding a Casual Association Exists 1. Collect all epidemiologic literature on the disorder 2. Identify study design. Stronger consideration to superior study designs, provided each study has sound methods 3. Assess study methods, including existence and degree of: a. Exposure assessment methods and potential biases b. Disease ascertainment methods and potential biases c. Absence of significant uncontrolled confounders; consideration of residual confounding. d. Addressing of other potential biases or fatal flaws e. Adequacy of biostatistical methods and analytical techniques 4. Ascertain statistical significance and degree to which chance may have produced results Chapters 3-4. Causal Assessment and Methodology. In: Guides to the Evaluation of Disease and Injury Causation. Melhorn, Talmage, Ackerman, Hyman (Eds). AMA, Steps for Concluding a Casual Association Exists 5. Assess studies using Updated Hill Criteria. Apply criteria to individual studies (especially 5a-5c) and to studies as a whole (5a-5l) a. Temporality g. Plausibility b. Strength of association h. Reversibility c. Dose-response relationship i. Prevention/elimination d. Consistency j. Experiment e. Coherence k. Analogy f. Specificity l. Predictive performance 6. Conclusion about degree to which a casual association is or not present Chapters 3-4. Causal Assessment and Methodology. In: Guides to the Evaluation of Disease and Injury Causation. Melhorn, Talmage, Ackerman, Hyman (Eds). AMA,

3 Table 4-4: Quality Scoring Scale Criteria Range of scores Clearly defined groups 0-10 Exposure measurements 0-10 Participation and dropout rates 0-10 Blinding of exposure measurements 0-10 Health outcomes measurements 0-10 Frequency of health outcomes assessments 0-10 Blinding of health outcomes assessments 0-10 Comparable groups adjustment for confounders 0-20 Bias 0-10 Temporality 0-10 Dose-response gradient 0-10 Strength of association 0-10 Psychological factors 0-10 Table 4-5: Study Design Weighting Factors Study Design Weighting Factor Prospective cohort 1.0 Retrospective cohort 0.60 Case-control 0.30 Cross-sectional 0.15 Ecological Causation: Strength of Evidence Definitions Evidence Level Very strong evidence (>500) or strong evidence ( ) Some evidence ( ) Definition 3 studies with sufficient methodological quality agree it is a risk factor, and RR>2.0 and 2 high-quality prospective cohort studies agree Does not qualify for strong evidence, yet 2 studies with sufficient quality that generally agree it is a risk factor, and RR >2.0 and 1 of studies is highquality prospective cohort study 9

4 Causation: Strength of Evidence Definitions Low risk evidence (usually ; see relative risk) Insufficient evidence (<100) Conflicted evidence No risk evidence 3 studies with sufficient quality agree risk is low, and RR <2.0, and 2 highquality prospective cohort studies agree Either no or few studies exist, but, methodologically corrected evidence score <100, and more studies required before potential risk factor can be evaluated Studies of equal quality disagree on risk, and no conclusion possible 3 studies with sufficient quality agree it is not a risk, and 2 high-quality prospective cohort studies agree Table 4-7: Strength of Evidence of Causation in Epidemiologic Studies Evidence Point value Very strong > 500 Strong Some Insufficient <100 Conflicted Insufficient risk Some conflicted evidence See insufficient evidence Chapters 3-4. Causal Assessment and Methodology. In: Guides to the Evaluation of Disease and Injury Causation. Melhorn, Talmage, Ackerman, Hyman (Eds). AMA, Comparison: 2 CTS studies Criteria Atroshi 07 Garg 12 Clearly defined groups Exposure measurements Participation and dropout rates Blinding of exposure measurements 0 10 Health outcomes measurements 4 10 Frequency of health outcomes assessments 0 10 Blinding of health outcomes assessments 0 10 Comparable groups adjustment for confounders 10/20 15/20 Bias 5 10 Temporality 0 10 Dose-response gradient 10 (Inv.) 9 Strength of association 5 (Neg.) 7.5 Psychological factors /140

5 Challenges Nothing s Perfect! Collection of all literature Judgment (argument) about which factor to weigh most strongly One fatal flaw could be under-emphasized Limited range of jobs How far can results be extrapolated? Discussion 14