Discordance between GOLD and peakVO2/kg-based CPET grading was common, particularly in patients with mild-to-moderate airflow obstruction, and was associated with age, adiposity, and cardiovascular comorbidity, with the discordance partly attributable to body-weight normalization inherent to peakVO2/kg.
Agreement between GOLD spirometry-based grading and peakVO2/kg-based CPET grading was slight, with exact grade concordance in fewer than one-third of patients.
The majority of COPD patients received a more severe disease grade from CPET-based grading than from GOLD spirometry-based grading.
Patients whose disease severity was upgraded by CPET relative to GOLD grading were older, had higher BMI, higher body fat percentage, higher fat mass, and were more likely to have cardiovascular comorbidity.
PeakVO2/kg was negatively correlated with fat mass, whereas peakVO2%pred was not, suggesting that body-weight normalization in peakVO2/kg contributes to grading discordance in patients with greater adiposity.
The authors recommend that peakVO2%pred, body composition, and other clinical and physiological findings should be considered alongside peakVO2/kg when interpreting CPET results in COPD patients.
This research compared two different ways of measuring how severe COPD (chronic obstructive pulmonary disease) is: the traditional lung function test (spirometry, used in the GOLD grading system) and cardiopulmonary exercise testing (CPET), which measures how much oxygen a person uses during exercise. In a study of 152 people with stable COPD, the two methods frequently disagreed — only about 31% of patients received the same severity grade from both tests. Most notably, 60.5% of patients were classified as having more severe disease by the CPET measure (peak oxygen uptake per kilogram of body weight, or peakVO2/kg) than by the lung function test, especially among those with mild or moderate airflow limitation. This research suggests that a key reason for this disagreement is how the CPET measure is calculated. Because peakVO2/kg divides oxygen uptake by body weight, people who carry more body fat naturally score lower — not necessarily because their heart and lungs are more impaired, but because fat tissue adds to body weight without contributing to oxygen use during exercise. The study found that peakVO2/kg decreased as fat mass increased, while an alternative CPET measure (peakVO2%pred, which compares a person's oxygen uptake to what would be predicted for someone their age and size) did not show this relationship. Patients who were reclassified as more severe by CPET were also older and more likely to have heart disease. This research suggests that CPET can reveal important information about exercise capacity that lung function tests alone may miss, but the results need careful interpretation — particularly in patients who are overweight or obese. Rather than relying on peakVO2/kg alone, clinicians are encouraged to also consider alternative CPET measures like peakVO2%pred, body composition data, and other clinical information when assessing COPD severity. The authors note these findings are preliminary and call for future studies to confirm them.
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Upload Your LabsYu C, Li Y, Qumu S, Xia J, Lei J, Li X, et al.. (2026). Cardiopulmonary Exercise Testing and Pulmonary Function for Assessing Chronic Obstructive Pulmonary Disease.. International journal of chronic obstructive pulmonary disease. https://doi.org/10.2147/COPD.S620471