Differences in classification of COPD patients into risk groups A-D: a cross-sectional study
Stefanie Zogg1, Selina Dürr, David Miedinger
1Medical University Clinic, Cantonal Hospital Baselland, Rheinstrasse 26, Liestal CH - 4410, Switzerland. stefanie.zogg@ksbl.ch.
BMC Research Notes
|August 24, 2014
Summary
Classifying chronic obstructive pulmonary disease (COPD) patients using the COPD Assessment Test (CAT) or modified Medical Research Council (mMRC) yields different risk group assignments. Physical activity, measured in daily steps, decreased across higher COPD risk groups.
Area of Science:
- Pulmonology
- Medical Research
- Clinical Trials
Background:
- The Global Initiative for Chronic Obstructive Lung Disease (GOLD) established a risk classification system (Groups A-D) for COPD in 2011.
- This system categorizes patients based on symptom burden and exacerbation risk to guide disease management.
- Variations in classification methods may impact patient stratification and subsequent treatment strategies.
Purpose of the Study:
- To evaluate the agreement between COPD risk group classifications using the COPD Assessment Test (CAT) and the modified Medical Research Council (mMRC) scale.
- To compare these classifications against objective measures of disease severity, including spirometry-defined grades and past-year exacerbation history.
- To examine the relationship between COPD risk groups and objectively measured daily physical activity levels.
Main Methods:
- Eighty-seven patients with stable COPD were categorized into GOLD risk groups A-D.
- Symptom burden was assessed using the CAT and mMRC questionnaires.
- Disease severity was determined by spirometry (GOLD grades I-IV), and the number of exacerbations in the preceding year was recorded.
- Interrater agreement was quantified using Cohen's Kappa statistic.
- Objective daily physical activity was measured using the SenseWear Mini armband.
Main Results:
- A significant discrepancy was observed in risk group allocation: 65.5% of patients fell into high-symptom groups (B and D) using CAT, compared to 37.9% using mMRC.
- Classification based on spirometry severity grades placed 20.7% in high-exacerbation risk groups (C and D), while past-year exacerbations identified only 9.2% in these groups.
- Interrater agreement was fair between CAT and mMRC (κ=0.21) and between severity grades and exacerbations (κ=0.31).
- A significant reduction in daily steps was noted in GOLD risk groups B and C+D compared to group A, irrespective of the classification tool used (p<0.01).
Conclusions:
- The choice of assessment tool (CAT vs. mMRC) and outcome measure (symptoms vs. exacerbations) significantly influences COPD risk group classification.
- Fair agreement exists between different classification methods, highlighting potential inconsistencies in patient stratification.
- Physical activity, as measured by daily steps, progressively declines with increasing COPD risk, underscoring the impact of disease severity on functional status.
