Should unpublished data be included in meta-analyses? Current convictions and controversies
Article Abstract:
Unpublished data should not be completely excluded from meta-analyses but should be subject to the same methodological review as published data before inclusion. Meta-analyses combine data from several studies and have become an increasingly important tool for summarizing and assessing scientific findings. Publication bias refers to the differential selection or submission of studies based on the strength or direction of the findings. Meta-analyses that exclude unpublished data could thus be seen as misleading. Of 150 meta-analyses, 46 included unpublished data. Of the meta-analysts and methodologists surveyed, 77.7% felt that unpublished studies should be included as did 46.9% of journal editors surveyed. One possible solution would be for meta-analysts to analyse data both with and without unpublished studies. If the analyses came to a similar conclusion, the meta-analysis would be that much stronger and vice versa. All studies included should be rigorously evaluated because even publication in a peer-reviewed is no guarantee of scientific quality.
Publication Name: JAMA, The Journal of the American Medical Association
Subject: Health
ISSN: 0098-7484
Year: 1993
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Determinants in Canadian health care workers of the decision to withdraw life support from the critically ill
Article Abstract:
Health care workers in intensive care units (ICUs) may make decisions about continuing life support based more on their own individual morals and beliefs than on patient characteristics. A survey of 1,361 attending physicians, house staff and nurses working in the ICUs of 37 Canadian hospitals revealed a great variation in attitudes toward treatment. Participants evaluated 12 patient scenarios and indicated their preferred treatment strategy from five choices, ranging from comfort measures (no life support) to aggressive management. There was only one scenario for which over half the respondents agreed on treatment. In eight of the scenarios, over 10% of those surveyed selected opposite extremes of care. Respondent characteristics significantly associated with level of care chosen were years since graduation, size of the ICU and geographic location. Significant patient characteristics included age, likelihood of survival, and prior cognitive function.
Publication Name: JAMA, The Journal of the American Medical Association
Subject: Health
ISSN: 0098-7484
Year: 1995
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Effects of dietary calcium supplementation on blood pressure: a meta-analysis of randomized controlled trials
Article Abstract:
Calcium supplements may lower blood pressure slightly in people with hypertension but it does not appear to have a significant effect in people with normal blood pressure. Researchers used meta-analysis to review 33 controlled clinical trials that studied the effect of calcium supplements on blood pressure. Overall, the studies included 1,214 people who took calcium supplements and 1,198 who did not. A pooled analysis of all the studies showed that calcium supplementation reduced systolic blood pressure by 1.27 mm Hg and diastolic blood pressure by .24 mm Hg. In the six studies that specifically labelled one group as hypertensive and the other as normotensive, calcium supplements reduced systolic blood pressure in the hypertensive participants by 4.3 mm Hg and diastolic pressure by 1.5 mm Hg. In the normotensive participants, systolic pressure dropped .27 mm Hg and diastolic pressure dropped .33 mm Hg.
Publication Name: JAMA, The Journal of the American Medical Association
Subject: Health
ISSN: 0098-7484
Year: 1996
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