3 parameters for cluster change in stable COPD patients
Cluster assignment has been maintained by most of the patients with chronic obstructive pulmonary disease (COPD) after 2 years of follow-up, according to a study. The principal driving parameters in those who change their cluster assignment include exercise tolerance, lung function and quality of life.
This study evaluated 521 smokers with COPD at baseline and 2 years later. At both evaluation periods, three different clusters were identified consistently: cluster A (of younger age, mild airway limitation, few symptoms), cluster B (intermediate) and cluster C (of older age, severe airway limitation and highly symptomatic).
After 2 years of follow-up, 70 percent of patients remained unchanged, while the rest changed from one cluster to another (20 percent from A to B; 15 percent from B to A; 15 percent B to C; 42 percent from C to B; and 8 percent from C to A).
The main parameters responsible for this cluster shift were 6-minute walking distance (6MWD), forced expiratory volume in 1 s (FEV1) % and COPD Assessment Test (CAT).
The following variables were evaluated in COPD patients at baseline and 2 years later: age, gender, pack-year history, body mass index, modified Medical Research Council scale, 6MWD, spirometry and CAT. Cluster analysis was used to conduct patient classification at baseline and 2 years later.
The investigators also explored each patient’s cluster variability after 2 years and its parameters associated with cluster change.
“Cluster analysis has been utilized to explore phenotypic heterogeneity in COPD,” the investigators said. “To date, little is known about the longitudinal variability of clusters in COPD patients.”