Study Questions Value of Randomized Drug Trials That Exclude Subjects with ‘Comorbidities’ Since They Do Not Reflect Reality

In structuring randomized controlled trials that target specific chronic medical conditions, researchers will, by necessity, come across a large number of individuals that suffer from comorbid conditions as well.

Clearly, when testing people with diabetes, hypertension, cardiovascular disease, elevated cholesterol, or similar medical disorders, it is likely that a significant percentage of the potential subjects will have also developed one or more of the other conditions.

In selecting participants in the trials, however, researchers will selectively exclude those with multiple conditions from the study by either not recruiting them or by not including the data relating to them if they are chosen to participate.

Thus, the clinical results upon which treatments are formulated or suggested simply do not reflect the typical patient who presents with the condition that was being studied. Primary care physicians may therefore not have an accurate model upon which to determine how a study’s findings apply to real patients.

This is precisely the issue tackled by a study published in the March/April issue of Annals of Family Medicine that evaluated whether randomized controlled trials which exclude patients with comorbidities is actually supporting clinical practice guidelines.

The study authors sought “to call attention to an issue of increasing relevance — comorbidity,” according to Dr. Martin Fortin of the department of family medicine at Sherbrooke University, Quebec, Canada.

“Results from our study suggest that randomized controlled trials targeting a chronic medical condition such as hypertension would most likely find a great many patients with comorbid conditions during the screening process,” the team wrote.

When trials exclude patients with comorbidities, or do not include data on them, the study authors wrote, physicians may be getting an inaccurate idea of how the drug affects the patients they treat, based on the randomized controlled trials data.

The high incidence of comorbid and multi-morbid conditions in today’s patients affects responsiveness to particular interventions as well as the occurrence of adverse effects. The study suggests that a narrow focus on particular diseases should give way to much broader analysis of various characteristics of health and their impact on individual patients as well as populations.

Taking hypertension as a basis for their analysis the researchers attempted to ascertain the prevalence of co-morbidities among primary-care patients with that condition who would meet the inclusion criteria in a randomized controlled targeting that disease.

The study examined data on 320 men and 660 women from an existing database of patients of family care physicians. The team then proceeded to apply the inclusion and exclusion criteria from five actual trials (involving hypertension) to the sample group. They considered patients who met the inclusion criteria for a trial to be eligible for that trial.

The researchers found 89% to 100% of the patients who were eligible for each of the trials had multiple chronic conditions. None of the actual trials stated how many patients with comorbidities were excluded after they met the inclusion criteria, although four of the five offered limited data on comorbidities related to hypertension.

Thus, the study authors believe that the lack of more detailed information on comorbidities is serious omission.

According to the study: “All coexistent diseases are potentially important when treatments target specific chronic diseases. For example, depression is a psychiatric comorbidity that randomized controlled trials targeting hypertension may consider irrelevant; however, depression in patients with hypertension can result in a difficult clinical course because depression may adversely affect the patients’ adherence to medication and self-care regimens.”

The study also noted that patients with various chronic conditions are often taking many different drugs in addition to the medication that was being studied. This factor could affect adherence to the regimen in a clinical trial. In addition, if patients on multiple medications are excluded, adverse reactions peculiar to situations of polypharmacy could be missed.

The team concluded that research results “intended to be applied in medical practice should take the complex reality of effective treatment of these patients into consideration.”

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