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Researchers investigated risk factors for acute COPD exacerbations to guide clinical decision-making for patients with a limited history of COPD.
Acute exacerbations of chronic obstructive pulmonary disease (AE-COPD) are not uncommon in patients living with COPD. Since these detrimental episodes of worsening disease symptoms deteriorate prognosis and initiate hospitalization, prognostic tools, such as clearly defined risk factors for AE-COPD, could help in the management of this disease. Unfortunately, when there is limited patient history of exacerbations, it can be difficult to identify risk factors.
Limited History of Exacerbations
To address this knowledge gap, Michael C. Ferrera, MD, and colleagues developed a study to identify risk factors for COPD exacerbations in patients with limited history. The researchers drew their study population from participants in the Genetic Epidemiology of COPD Study (COPDGene), identifying those without a history of exacerbation within the previous year. Dr. Ferrera and colleagues published their findings in the Annals of the American Thoracic Society.
A total of 1,528 patients met the study criteria. Participants had a history of smoking and COPD, which researchers defined as forced expiratory volume in 1 second (FEV1/forced vital capacity < 0.70). The mean age of the participants was 69 years (SD, 8 years); 58.1% were men, 80.7% were White, and 66.3% were former consumers of tobacco products. At the time of the second visit, 56% of participants did not use inhaled medications.
The patients also had no AE-COPD on record in the year before their second COPDGene study visit, and they took part in at least one longitudinal follow-up questionnaire in the following 36 months. During the study period, 508 participants experienced at least one moderate or severe exacerbation.
Dr. Ferrara and colleagues applied univariable and multivariable zero-inflated negative binomial regression models to isolate risk factors associated with enhanced exacerbation rates. The researchers rounded the regression coefficient (β) of each identified risk factor to the nearest 0.25 and integrated it into a graduated risk score.
Risk Factors Identified
Readily available risk factors included self-reported history of gastroesophageal reflux disease (GERD) (rate ratio [RR], 1.26; 95% CI, 1.02–1.56; P=0.03), self-reported history of chronic bronchitis (RR,1.64; 95% CI, 1.30–2.08; P<0.001), and Modified Medical Research Council (mMRC) dyspnea scale rating greater than 2 (RR, 1.99; 95% CI, 1.62–2.46; P<0.001). These risk factors were all associated with an elevated rate of moderate or severe exacerbations in univariable analyses.
The researchers also identified risk factors that primary care physicians may not usually consider. These included a COPD Assessment Test (CAT) score greater than 10 (RR, 2.28; 95% CI, 1.83–2.86; P<0.001) and lower FEV1% predicted (RR, 1.40 per 220%; 95% CI, 1.22–1.60; P<0.001).
In the first graduated model, GERD, chronic bronchitis, and mMRC were incorporated to attain a risk score, and resource variables, including CAT and spirometry, were added in stepwise progression. A higher score in the model was associated with an increased probability of exacerbations (RR, 1.37; 95% CI,1.29–1.45; P<0.001). A 1-point climb in score was associated with a 29% increase in the rate of exacerbations in the 36-month period.
Researchers added a CAT score greater than 10 to the model and found that a higher score was also associated with a higher risk for exacerbations (RR per 1-point score increase,1.34; 95% CI, 1.27–1.41; P<0.001). When FEV1% predicted was added, a high score in this model also correlated with an increased risk for exacerbations (RR per 1-point score increase, 1.30; 95% CI,1.25–1.36; P<0.001).
“In patients with COPD but without a recent history of exacerbations, risk factors such as GERD, chronic bronchitis, high symptom burden, and lower lung function are associated with an increased risk for future exacerbation. These risk factors can be collated into a simple risk score, which can be used in clinical practice,” Dr. Ferrera and colleagues concluded.
