About 10 years ago, researchers validated the BODE index—which stands for BMI, airflow obstruction, dyspnea, and exercise capacity—as a prognostic mortality risk tool for patients with COPD (Table 1). “The development and validation of the BODE index was an effort to more fully characterize disease severity in patients with COPD,” explains Melissa H. Roberts, MS, PhD. “It captures not only the clinical measurements of COPD through a lung function test, but also some of the systemic effects of the disease that can appear in patients with COPD.”
Since 2004, many studies have demonstrated that the BODE index is a more accurate predictor of mortality among patients with COPD than lung function alone. Additional analyses have shown that the index can also serve as a good predictor of severe COPD exacerbations resulting in hospitalization. Over this same stretch of time, other studies have assessed modified versions of the BODE index to determine if other measurements may offer additional value, but these analyses have had mixed results.
A Simpler Approach
Although the BODE index has proven to be useful, research has suggested that implementing use of the tool can be challenging, oftentimes proving to be impractical if patients are debilitated. Recently, Dr. Roberts and colleagues examined a simplified, quasi-BODE index and published their results in the American Journal of Epidemiology. “The spirometry test for measuring FEV1 to determine airway obstruction and the 6-minute walk test for measuring exercise capacity are not always easy to obtain, especially in patients who are not ambulatory,” explains Dr. Roberts. “A substantial percentage of patients are unable to complete either or both of these tests. In our study, we replaced spirometry with the peak expiratory flow (PEF) test, an inexpensive test that can be completed by most patients and even in primary care settings.”
The quasi-BODE index also replaced the 6-minute walk test with physical functioning and symptom information. This was more readily found in survey data that included questions about difficulty walking or lifting weights, trouble with shortness of breath, and other factors. “These are questions that can be answered during a short patient visit and overall assessment,” Dr. Roberts says. “The modified index could be used to assess mortality risk in patients without COPD and also help identify COPD patients with a higher risk of mortality.”
The prognostic ability of the quasi-BODE index was tested in logistic regression models for mortality in a 2-year post-survey period among patients aged 50 and older. A BMI of 21 kg/m2 or less, lower percentages of predicted PEF, shortness of breath, difficulty lifting or carrying more than 10 lbs, and difficulty walking one block were each associated with an increased risk of 2-year mortality (Table 2).
Whereas the original BODE index had a maximum possible value of 10, the quasi-BODE index has a maximum possible value of 8. Dr. Roberts and colleagues noted that only 1% of their study participants had quasi-BODE index scores higher than 5. Each unit increase in the quasi-BODE index score was associated with a multiplicative 50% increase in mortality risk. The instrument was predictive of mortality in older patients with and without COPD, including those with severe physical limitations. It was also predictive of mortality when used alone or in conjunction with gender, age, and other morbidity information.
“We envision the quasi-BODE index as being an easy-to-administer screening tool to identify patients both with and without COPD who are at risk,” says Dr. Roberts. “This can be of great benefit because clinicians can then modify treatment and lifestyle to lengthen their survival, improve quality of life, or both.” She notes that some of the elements of the quasi-BODE index score are potentially modifiable, including difficulty with walking a block or carrying 10 lbs. Studies have shown that patients who undergo pulmonary or inpatient rehabilitation, or even small amounts of exercise in a nursing or retirement home, tend to have lower risks for adverse outcomes in the future.
While the results were encouraging, Dr. Roberts says her research team’s findings could be strengthened with more studies that replicate and validate their observations. “We would also like to see if any additional measures could further improve upon the performance of the quasi-BODE index,” she adds.
The future of the quasi-BODE index appears promising, Dr. Roberts says. “This is a tool that incorporates patient-reported outcomes and patient perceptions about their disease in conjunction with a few objective measures—such as PEF and BMI—that, taken together, are a strong indicator of mortality. Improving our ability to assess multiple aspects of a patient will provide a better picture of their COPD-related mortality risk than any single measure.”
Roberts M, Mapel D, Bruse S, et al. Development of a modified BODE index as a mortality risk measure among older adults with and without chronic obstructive pulmonary disease. Am J Epidemiol. 2013;178:1150-1160. Available at http://aje.oxfordjournals.org/content/178/7/1150.
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