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Review
. 2012;7(8):e41601.
doi: 10.1371/journal.pone.0041601. Epub 2012 Aug 3.

Informing evidence-based decision-making for patients with comorbidity: availability of necessary information in clinical trials for chronic diseases

Cynthia M Boyd  1 , Daniela Vollenweider, Milo A Puhan
Affiliations
Review

Informing evidence-based decision-making for patients with comorbidity: availability of necessary information in clinical trials for chronic diseases

Cynthia M Boyd et al. PLoS One. 2012.

Abstract

Background: The population with multiple chronic conditions is growing. Prior studies indicate that patients with comorbidities are frequently excluded from trials but do not address whether information is available in trials to draw conclusions about treatment effects for these patients.

Methods and findings: We conducted a literature survey of trials from 11 Cochrane Reviews for four chronic diseases (diabetes, heart failure, chronic obstructive pulmonary disease, and stroke). The Cochrane Reviews systematically identified and summarized trials on the effectiveness of diuretics, metformin, anticoagulants, longacting beta-agonists alone or in combination with inhaled corticosteroids, lipid lowering agents, exercise and diet. Eligible studies were reports of trials included in the Cochrane reviews and additional papers that described the methods of these trials. We assessed the exclusion and inclusion of people with comorbidities, the reporting of comorbidities, and whether comorbidities were considered as potential modifiers of treatment effects. Overall, the replicability of both the inclusion criteria (mean [standard deviation (SD)]: 6.0 (2.1), range (min-max): 1-9.5) and exclusion criteria (mean(SD): 5.3 (2.1), range: 1-9.5) was only moderate. Trials excluded patients with many common comorbidities. The proportion of exclusions for comorbidities ranged from 0-42 percent for heart failure, 0-55 percent for COPD, 0-44 percent for diabetes, and 0-39 percent for stroke. Seventy of the 161 trials (43.5%) described the prevalence of any comorbidity among participants with the index disease. The reporting of comorbidities in trials was very limited, in terms of reporting an operational definition and method of ascertainment for the presence of comorbidity and treatments for the comorbidity. It was even less common that the trials assessed whether comorbidities were potential modifiers of treatment effects.

Conclusions: Comorbidities receive little attention in chronic disease trials. Given the public health importance of people with multiple chronic conditions, trials should better report on comorbidities and assess the effect comorbidities have on treatment outcomes.

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Conflict of interest statement

Competing Interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare that (1) CMB and DPV had support from Robert Wood Johnson Foundation Physician Faculty Scholars Program for the submitted work and CB had support from the Paul Beeson Career Development Award Program (NIA K23 AG032910, AFAR, The John A. Hartford Foundation, The Atlantic Philanthropies, The Starr Foundation and an anonymous donor), and AHRQ R21 HS018597-01; (2) CMB, DV, and MAP have no relationships with companies that might have an interest in the submitted work in the previous 3 years; (3) their spouses, partners, or children have no financial relationships that may be relevant to the submitted work; and (4) CMB, MAP, and DPV have no non-financial interests that may be relevant to the submitted work. This does not alter the authors' adherence to all the PLoS ONE policies on sharing data and materials.

Figures

Figure 1
Figure 1. Proportion of heart failure trials where patients with specific comorbidities were excluded.
Figure 2
Figure 2. Proportion of chronic obstructive pulmonary disease (COPD) trials where patients with specific comorbidities were excluded.
Figure 3
Figure 3. Proportion of diabetes trials where patients with specific comorbidities were excluded.
Figure 4
Figure 4. Proportion of stroke trials where patients with specific comorbidities were excluded.
See this image and copyright information in PMC

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