We selected the top 2 general medical journals based on their year 2000 impact factor as ranked by ISI Journal Citation Reports.6
Data from both the print and electronic 2001 issues of The New England Journal of Medicine (NEJM) and The Journal of the American Medical Association (JAMA)7,8
were analyzed for trends in sources of funding, areas of investigation, COI, and presentation of results. All monetary descriptions are in U.S. dollars.
In NEJM, we analyze only manuscripts defined by the journal as “Original Reports.” In JAMA, we analyze 190 “Original Contribution” articles, and an additional 15 in the following subsection headings: 3 “Caring for critically ill patients,” 3 “Clinical cardiology,” 2 “Clinical evaluation,” 4 “Clinical investigation,” 2 “Preliminary communications,” and 1 “Toward optimal laboratory use.” Editorials, reviews, commentaries, case reports, and brief reports from both journals were excluded.
We use author descriptions to classify study design, number of subjects per study, and funding source. In cases where author/s did not define study design, we use the definitions in Abramson for categorization.9
Both journals request authors to disclose financial relationships with companies whose product they review in the manuscript. Sponsor and type of financial support were in most cases disclosed by authors. The authors of 33 studies from both journals combined did not disclose financial relationships. All 33 studies were categorized as studies without financial associations. Seven studies in which the authors only provide the name of a financial sponsor, but not a description of the financial support, were categorized as “grant/funding.”
We were unable to find broad consensus for any single definition of COI. We therefore use 3 definitions for COI in this paper: 1) a broadly defined criterion, 2) the criterion used by The International Council of Medical Journal Editors (ICMJE), and 3) a criterion defined by the authors.
The broadly defined COI criterion is defined as all financial relationships with companies whose products the researchers are evaluating in the manuscript, except for studies only supported by free drugs and equipment.
Second, we use the COI criterion set forth by the ICMJE.10
This “narrowly defined” criterion refers to those financial relationships specifically cited as the most severe examples of conflict of interest that include consultancy, employment, stock ownership, patent licensing, and honoraria. This criterion excludes financial relationships based on grants, both general and specific funding, awards, fellowships, free drugs or equipment, and authors serving as speakers or on an advisory board.
Third, we use an internal definition of COI. Neither of the above criteria address the commercial components of the studies. A study must meet each of the following 4 criteria: 1a) one or more authors have financial associations with a private corporation in the form of grants, unspecified funding, consultancy, employment, stock ownership, or honoraria; and/or b) have a personal financial interest in the study because of a patent license in which an author is eligible to receive royalties or from personal investments. Free drugs and equipment, awards, fellowships, and serving on advisory boards or as speakers do not constitute COI in this definition; 2) drug/treatment/product reviewed by the author/s is manufactured by the funding corporation, or is in the same retail class11
as a drug manufactured by a sponsoring competitor; 3) product(s) reviewed by author(s) must have current or near future commercial potential (i.e., sold for profit); and 4) presentation of main findings support commercial product, negate competitor's product, advocate cost benefit, and/or show product has a potential commercial value (demand, size, and growth).
To assess the association between COI and reported study findings, we classified the presentation of the results as follows: positive, mixed, negative, or other.
Positive results include studies that show a statistically significant (P < .05) clinical benefit from a treatment or absence of suspected side effects (P > .05), achieve statistically valid equivalence comparable to commonly used therapies, or support their product by observing side effects in a competitive product or insignificant association with intended outcome from use of competitor's product (P > .05; N = 4 studies for latter). Mixed results include studies noting both clinical benefits from a treatment and presence of significant adverse effects (both P < .05). Negative results include studies that report the absence of clinical benefits (P > .05) and/or evidence for numerous adverse effects (P < .05). “Other” category includes studies that are observational or cross-sectional emphasizing frequency and distribution rather than comparison between groups; trends in medical services and product usage; drug discontinuation protocol; or studies whose significance is yet unclear because it is a preliminary or pilot study.
We use SAS for Windows (version 8.0; SAS Institute, Inc., Cary, NC) for the statistical analysis. We use χ2 tests for analysis of categorical variables. We fit a multiple logistic regression model including potential predictors to estimate adjusted odds ratios (OR) for reported positive/negative results and COI. We use both ICMJE and author-defined criteria for COI when fitting our model. Adjusted odds ratios for all treatment-related studies and drug-related studies, respectively, were calculated. The model included the following variables: sample size, study design, and country of origin of primary authors. To evaluate the association between positive results and COI, the categories used in were aggregated (mixed, negative, and other). The same procedure was conducted to evaluate the association between negative results and COI (positive, mixed, and other were aggregated). A two-sided P value less than .05 was considered statistically significant.
Reported Study Outcomes Among Original Manuscripts by Conflict of Interest Criteria, and Study Focus The New England Journal of Medicine and The Journal of the American Medical Association (2001)