Comparison of stability of the GOLD and STAR lung function classification for chronic obstructive pulmonary disease

Background The diagnosis of chronic obstructive pulmonary disease (COPD) typically relies on spirometric measurements. The Staging of Airflow Obstruction by Ratio (STAR) classification, a newly proposed system for grading the severity of pulmonary function, has been suggested as a potentially better predictor of outcomes than other classifications. However, the long-term stability of the STAR classification, especially in comparison to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) classification, remains unclear. Methods In this retrospective cohort study, we analysed data from 622 patients with COPD, enrolled in a pay-for-performance programme at two university hospitals in Taiwan. Patients were classified according to the GOLD and STAR classifications, based on post-bronchodilator spirometry results. The study assessed the agreement between these classifications and the stability of each over a 3-year period, categorising patients into four patterns: no change (stable stage throughout), progression (persistent shift to severe stage), instability (fluctuating between higher and lower stages) and reversal (sustained improvement to a less severe stage). Results The STAR classification system identified a higher proportion of patients with instability or reversal patterns (42.1%) compared with the GOLD classification (31.0%). While fair coherence was noted between the two classifications over 3 years, the STAR classification demonstrated greater variability. Compared with the GOLD classification, the STAR classification exhibited a higher proportion of instability or reversal patterns in stage 2 but a lower proportion of these patterns in stage 4. Conclusion Compared with the GOLD classification, the STAR classification demonstrated higher instability and reversal patterns, suggesting the need for careful consideration for its use in long-term COPD management. Further research is required to explore the clinical implications of these findings and to refine the use of these classifications.