It appears that some progress has been made by CPGs developers to improve transparency through disclosures by CPG authors over the last two decades. Choudhry and colleagues 
reported that only 2 of 44 CPGs published between 1991 and 1999 included author disclosures. Similarly, Papanikolaou and coauthors 
reported that only seven of 40 guidelines published in six major clinical journals in 1999 provided disclosures. Tregear 
reported that the proportion of summaries in NGC with financial relationships reported increased from about 20% in 1999 to 50% in 2006, although these summaries contain information supplied by guideline developers in response to a specific request for COI information, and thus may be more complete than information contained only within the guideline document. More recently, Neuman and colleagues 
reported that 64% of 14 CPGs on diabetes or hyperlipidemia provided public author disclosures and 17 recent CPGs by the American college of Cardiology and the American Heart Association all provided disclosures 
. The current study also suggests that disclosure rates, although still suboptimal, have improved.
This apparent improvement in disclosure rates may be attributed in part to increased awareness of the potential importance of COI in primary medical research and in derivative products such as systematic reviews and clinical practice guidelines 
. There have been major efforts in the last 5 years to devise and update policies on COI disclosure and management by journals, academic institutions, government agencies, and professional organizations 
. In 2011 the IOM released a report with standards for guideline development based on an expert consensus process and evidence when available 
. One of the eight standards focuses on the management of COI and a second standard relates to the composition of the guideline development group. The IOM recommends disclosure of all potential and confirmed members of guideline panels, divestment of financial interests that could be affected by the guideline, exclusion (when possible) of individuals with COI, and a multidisciplinary and balanced guideline panel. Guideline organizations are beginning to incorporate these standards into their processes and policies 
and thus disclosure rates and guideline author COI may continue to improve.
Disclosures of COI by CPG panel members should be readily available to all users of a guideline in order to assess the risk of bias and the credibility of the guideline. It is therefore concerning that 42% of guidelines with disclosures did not make those disclosures available in the public domain. It is also not sufficient in our view to have disclosures only in the NGC summary and not in the CPG itself, as many users will not access the summary.
We report a lower proportion of conflicted CPG authors than have prior studies 
. In two recent studies examining small cohorts of CPGs 
, the percentage of authors with COI was 56% 
and 65% 
(among authors with publically available disclosures). Older studies report even higher rates of COI among guideline panel authors 
It is difficult to compare rates of COI for panel members across guidelines, however. Studies examining rates of COI in CPGs generally involve small, select cohorts with variations in publication sites (peer reviewed journal or web-based), policies on public availability of disclosures, disclosure forms and instructions (particularly relevance of the disclosure to the content of the CPG), and management of disclosed conflicts 
Although rates of disclosure of COI may be improving, a significant proportion of CPGs are developed by panels with one or more authors with a COI. There are likely a number of factors contributing to these continued high rates. Industry accounts for more than half of biomedical research funding and is continuing to increase in proportion to other funding sources 
, so clinical experts who conduct research and who participate in guideline development may be receiving significant funding from industry. Guideline authors who are asked to complete disclosure forms may be providing more complete and accurate disclosures in view of an increased awareness of COI, anticipation of scrutiny by journal editors and readers, and the use of the International Committee of medical Journal Editors (ICMJE) standardized disclosure form 
. Guidelines on specialized medical treatments may recruit from a small number of individuals with the relevant expertise, such that involving unconflicted individuals may not be possible.
Several factors were noted to be associated with whether or not CPGs had author disclosures. Journals with impact factors less than five had disclosures less commonly than CPGs that were not published in journals, suggesting that these journals either did not have COI polices or did not adhere to existing policies. Guidelines produced by Canadian organizations were more likely to have disclosures than US organizations, suggesting room for improvement among US-based organizations. Disclosures do appear to be occurring more frequently in later years of our 5-year examination, suggesting that positive changes are occurring.
CPGs published in journals with an impact factor greater than five were associated with an increased proportion of authors with COI. The reasons for this are unclear, but in addition to actually having more conflicts, authors might be more consistent in reporting COI in these journals due to the use of ICMJE forms, author experience, journal editor attention and pressure, and policy-specific influences such as a requirement to update COI disclosures periodically.
This study focuses on disclosures of COI by CPGs authors, however, the central issue for guideline quality is the risk of bias and the diminished credibility related to the secondary interests held by guideline developers. The relationship between disclosures and biased recommendations in CPGs is complex and poorly understood. The effect of COI on conclusions in CPGs is unknown 
as also is the effect of disclosing COI on the authors and the users of CPGs. We did not examine the management of disclosures for each of the CPGs in our cohort. It is possible that some of the effects of the disclosed conflicts were mitigated with procedures and approaches carried out by each organization during CPG development.
There are limitations to our approach. Although we examined COI statements from both the CPG itself and the statements provided to the NGC, disclosures in publications may not always be accurate 
, and the information in NGC may have limitations reflecting the quality of source documents used to determine COI 
. Additionally, we did not request author disclosures from organizations that did not provide these disclosures in the public domain as these were usually listed as available to members of that organization only. We examined all authors or panel members for each guideline, irrespective of their role on each panel; it is possible that the chair or co-chair of each guideline group might have played a dominant role in deliberations, and thus their COI might be more important than for other panel members. We did not examine the sources of funding for development of each CPG, so it is possible that funders may also have had a role in formulating recommendations in CPGs.
Our findings may be generalizable to other guidelines within the NGC, given our random, 10% sample. Applicability of our findings to CPGs not contained within NGC may be limited, however. For example, guidelines not published in English or those without an underlying systematic review may have different rates of disclosure and COI than those in our cohort.
Although financial interests are usually the most obvious, intellectual interests are increasingly recognized and may be powerful motivators for researchers, systematic reviewers, and guideline authors 
. Intellectual COI has been defined as “academic activities that create the potential for an attachment to a specific point of view that could unduly affect an individual’s judgment about a specific recommendation” 
. Intellectual interests include benefits the advancement of medical science, career advancement, fulfillment of a desire to do good, opportunity to publish, notoriety, future success in obtaining grant funding for research, and increased sense of self-worth 
. Very few CPGs in our cohort disclosed nonfinancial COI and future efforts in COI transparency need to address this.
It is clear that much improvement is still needed in the rates of disclosure of author COI, in the public availability of that information, and in the unacceptably high rates of COI among guideline authors. CPGs can be an important tool for improving patient care, and as such, continued efforts are needed to optimize their quality by increased transparency and by minimizing potential sources of bias.