American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Aug 2017
Classification of Airflow Limitation Based on Z-score Underestimates Mortality in Patients with Chronic Obstructive Pulmonary Disease.
Global Lung Function Initiative recommends reporting lung function measures as z-score, and a classification of airflow limitation (AL) based on this parameter has recently been proposed. ⋯ In patients with COPD, the AL classification based on z-score predicts worse mortality than those based on percentage of predicted. It is possible that the z-score underestimates AL severity in patients older than 60 years of age with severe functional impairment.