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Methodological Issues in Systematic Review - Formulating Questions -. Joseph Lau, MD Tufts Medical Center EPC AHRQ Annual Meeting September 10, 2008. Analytic framework for omega-3 FA intake and CVD. Specific Key Questions.
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Methodological Issues in Systematic Review- Formulating Questions - Joseph Lau, MD Tufts Medical Center EPC AHRQ Annual Meeting September 10, 2008
Specific Key Questions • What is the efficacy or association of omega-3 fatty acids (DHA, EPA or ALA supplements, and fish consumption) in reducing CVD events (including all-cause mortality, CVD mortality, non-fatal CVD events, and new diagnosis of CVD)? In patients without known CVD (primary prevention) and with known CVD (secondary prevention).
Specific Key Questions 2. Relative effects of omega-3 fatty acid sources, with specific emphasis on compositions, dosages, the ratio of omega-6 to omega-3 fatty acids, and potential interactions due to duration of intervention or exposure. • What adverse events related to omega-3 fatty acid dietary supplements are reported in studies?
Participants • Primary Prevention - patients without prior history of cardiovascular disease • Country • Background diet • Secondary Prevention – patients with prior history of cardiovascular disease
Interventions • Fish • Different kinds, preparation, amount, how intake was estimated • Fish oil supplements • Eicosapentaenoic acid (EPA) / Docosahexaenoic acid (DHA) • α-linolenic acid [ALA] (walnut, canola oil, flax seed, etc.)
Outcomes (endpoints) • Clinical outcomes (events) • Overall mortality • Stroke • Myocardial infarction • Sudden death • revascularization • Surrogate/intermediate outcomes (biomarkers, measurements) • Blood pressure • Lipid levels
The PICO method to formulate research question on interventions
Study design • RCT • Cohort • Case-control • Cross-sectional • Other criteria • Study size • Year, language, etc
Additional inclusion criteria • Published English language literature • Experimental or observational studies • Reported original CVD outcome data and evaluated any potential source of omega-3 fatty acids • At least 5 human subjects • At least 1-year duration
Issues in formulating a question • Narrow versus broad (for individual or population) • Clinically meaningful and useful (based on sound biological and epidemiological principles) • Very broadly defined questions may be criticized for mixing apples and oranges • Very narrowly focused questions may have no data or have limited generalizability and sometimes may lead to misinterpretations