Financial ties between health professionals and industry may unduly influence professional judgments and some researchers have suggested that widening disease definitions may be one driver of over-diagnosis, bringing potentially unnecessary labeling and harm. We aimed to identify guidelines in which disease definitions were changed, to assess whether any proposed changes would increase the numbers of individuals considered to have the disease, whether potential harms of expanding disease definitions were investigated, and the extent of members' industry ties.
Methods and Findings
We undertook a cross-sectional study of the most recent publication between 2000 and 2013 from national and international guideline panels making decisions about definitions or diagnostic criteria for common conditions in the United States. We assessed whether proposed changes widened or narrowed disease definitions, rationales offered, mention of potential harms of those changes, and the nature and extent of disclosed ties between members and pharmaceutical or device companies.
Of 16 publications on 14 common conditions, ten proposed changes widening and one narrowing definitions. For five, impact was unclear. Widening fell into three categories: creating “pre-disease”; lowering diagnostic thresholds; and proposing earlier or different diagnostic methods. Rationales included standardising diagnostic criteria and new evidence about risks for people previously considered to not have the disease. No publication included rigorous assessment of potential harms of proposed changes.
Among 14 panels with disclosures, the average proportion of members with industry ties was 75%. Twelve were chaired by people with ties. For members with ties, the median number of companies to which they had ties was seven. Companies with ties to the highest proportions of members were active in the relevant therapeutic area. Limitations arise from reliance on only disclosed ties, and exclusion of conditions too broad to enable analysis of single panel publications.
For the common conditions studied, a majority of panels proposed changes to disease definitions that increased the number of individuals considered to have the disease, none reported rigorous assessment of potential harms of that widening, and most had a majority of members disclosing financial ties to pharmaceutical companies.
Please see later in the article for the Editors' Summary
Health professionals generally base their diagnosis of physical and mental disorders among their patients on disease definitions and diagnostic thresholds that are drawn up by expert panels and published as statements or as part of clinical practice guidelines. These disease definitions and diagnostic thresholds are reviewed and updated in response to changes in disease detection methods, treatments, medical knowledge, and, in the case of mental illness, changes in cultural norms. Sometimes, the review process widens disease definitions and lowers diagnostic thresholds. Such changes can be beneficial. For example, they might ensure that life-threatening conditions are diagnosed early when they are still treatable. But the widening of disease definitions can also lead to over-diagnosis—the diagnosis of a condition in a healthy individual that will never cause any symptoms and won't lead to an early death. Over-diagnosis can unnecessarily label people as ill, harm healthy individuals by exposing them to treatments they do not need, and waste resources that could be used to treat or prevent “genuine” illness.
Why Was This Study Done?
In recent years, evidence for widespread financial and non-financial ties between pharmaceutical companies and the health professionals involved in writing clinical practice guidelines has increased, and concern that these links may influence professional judgments has grown. As a result, a 2011 report from the US Institute of Medicine (IOM) recommended that, whenever possible, guideline developers should not have conflicts of interest, that a minority of the panel members involved in guideline development should have conflicts of interest, and that the chairs of these panels should be free of conflicts. Much less is known, however, about the ties between industry and the health professionals involved in reviewing disease definitions and whether these ties might in some way contribute to over-diagnosis. In this cross-sectional study (an investigation that takes a snapshot of a situation at a single time point), the researchers identify panels that have recently made decisions about definitions or diagnostic thresholds for conditions that are common in the US and describe the industry ties among the panel members and the changes in disease definitions proposed by the panels.
What Did the Researchers Do and Find?
The researchers identified 16 publications in which expert panels proposed changes to the disease definitions and diagnostic criteria for 14 conditions that are common in the US such as hypertension (high blood pressure) and Alzheimer disease. The proposed changes widened the disease definition for ten diseases, narrowed it for one disease, and had an unclear impact for five diseases. Reasons included in the publications for changing disease definitions included new evidence of risk for people previously considered normal (pre-hypertension) and the emergence of new biomarkers, tests, or treatments (Alzheimer disease). Only six of the panels mentioned possible harms of the proposed changes and none appeared to rigorously assess the downsides of expanding definitions. Of the 15 panels involved in the publications (one panel produced two publications), 12 included members who disclosed financial ties to multiple companies. Notably, the commonest industrial ties among these panels were to companies marketing drugs for the disease being considered by that panel. On average, 75% of panel members disclosed industry ties (range 0% to 100%) to a median of seven companies each. Moreover, similar proportions of panel members disclosed industry ties in publications released before and after the 2011 IOM report.
What Do These Findings Mean?
These findings show that, for the conditions studied, most panels considering disease definitions and diagnostic criteria proposed changes that widened disease definitions and that financial ties with pharmaceutical companies with direct interests in the therapeutic area covered by the panel were common among panel members. Because this study does not include a comparison group, these findings do not establish a causal link between industry ties and proposals to change disease definitions. Moreover, because the study concentrates on a subset of common diseases in the US setting, the generalizability of these findings is limited. Despite these and other study limitations, these findings provide new information about the ties between industry and influential medical professionals and raise questions about the current processes of disease definition. Future research, the researchers suggest, should investigate how disease definitions change over time, how much money panel members receive from industry, and how panel proposals affect the potential market of sponsors. Finally it should aim to design new processes for reviewing disease definitions that are free from potential conflicts of interest.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001500.
A PLOS Medicine Research Article by Knüppel et al. assesses the representation of ethical issues in general clinical practice guidelines on dementia care
Wikipedia has a page on medical diagnosis (note: Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
An article on over-diagnosis by two of the study authors is available; an international conference on preventing over-diagnosis will take place this September
The 2011 US Institute of Medicine report Clinical Practice Guidelines We Can Trust is available
A PLOS Medicine
Essay by Lisa Cosgrove and Sheldon Krimsky discusses the financial ties with industry of panel members involved in the preparation of the latest revision of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM), which provides standard criteria for the classification of mental disorders