Determining What Outcomes Are Important In Diabetes Trials

Editor's Choice
Main Category: Diabetes
Also Included In: Clinical Trials / Drug Trials;  Public Health
Article Date: 03 Jun 2008 - 13:00 PDT

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According to a study published in the June 4 issue of JAMA, only about 20% of ongoing randomized clinical trials (RCTs) in diabetes consider primary outcomes that patients find important- notably illness, pain, effect on function, and death.

Gunjan Y. Gandhi, M.D., M.Sc., and M. Hassan Murad, M.D., M.P.H. (Mayo Clinic, Rochester, Minn.) and colleagues wonder if diabetes trials will be more informative to both patients and clinicians. Since RCTs have not measured the effect of diabetes interventions on outcomes important to patients such as quality of life and death, there are concerns about the safety and efficacy of these interventions.

Combing through databases of large public clinical trials, the researchers selected several that were in phases 2 through 4 and enrolled patients with diabetes. Their focus was to systematically establish the degree to which ongoing and future registered RCTs take into consideration outcomes that are important to patients. They found 2,019 RCTs, but narrowed down the initial group to only 1,054 due to eligibility requirements. Half of the trials (527) were randomly selected, and the analysis was performed on 436 trials registered since registration became mandatory (in 2004). Of the 436, 24 had not started enrollment (6%), 109 were actively enrolling (25%), and 303 had completed enrollment (69%).

For each study, reviewers collected data pertaining to study characteristic and noted the measured outcomes. They also classified outcomes by type:

• Physiological outcomes, such as insulin and C-peptide levels,
• Surrogate outcomes, such as cholesterol levels and worsening kidney function (that may increase the risk of some patient-important outcomes), and
• Patient-important outcomes, such as illness, pain, function, and death

In 18% of RCTs, primary outcomes were categorized as patient-important. This compares to 16% labeled as physiological or laboratory outcomes and 61% labeled as surrogate outcomes. In 46% of RCTs, patient-important outcomes were noted of primary or secondary importance.

Gandhi and colleagues also found that larger trials and longer trials were independent predictors of a study's focusing on patient-important outcomes. Trials of type 2 diabetes patients, however, were found to be significantly less likely to contain primary outcomes that were considered patient-important. Trial length and trial phase (phase 3 or 4 compared to phase 2) were significant predictors of patient-important outcomes as primary and secondary outcomes.

The authors explain that, "The importance of our findings is that (1) without pooling, the individual diabetes trials will largely fail in providing information about the effect of interventions on patient-important outcomes; and (2) trials that are planning to measure patient-important outcomes as secondary end points need to overcome the temptation to selectively report outcomes with statistically significant results as well as to report these findings transparently and carefully. Journals also may need to publish the less-than-interesting results to enable meta-analyses of these results to produce precise enough estimates that can guide practice."

They conclude: "We believe the time has come for a broad consensus on a standard set of important outcomes for patients in diabetes trials, similar to the Outcome Measures in Rheumatology (OMERACT) initiative. The OMERACT approach allows for the uniform measurement of outcomes in RCTs with emphasis on outcomes that experts-and ultimately patients-thought would better capture the experience of rheumatological conditions."

Patient-Important Outcomes in Registered Diabetes Trials
Gunjan Y. Gandhi; M. Hassan Murad; Akira Fujiyoshi; Rebecca J. Mullan; David N. Flynn; Mohamed B. Elamin; Brian A. Swiglo; William L. Isley; Gordon H. Guyatt; Victor M. Montori
JAMA (2008). 299[21]:2543-2549.
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Written by: Peter M Crosta
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