To the Editor The discriminative accuracy of various FEV1:FVC fixed thresholds for predicting COPD-related hospitalization and mortality was evaluated using data from 4 US general population–based cohorts with a median follow-up of 15 years.1 The authors defined the optimal fixed FEV1:FVC threshold by the best discrimination for COPD-related events as indexed using the Harrell C statistic from unadjusted Cox proportional hazards models. The authors further determined the significance of differences in C statistics with respect to FEV1:FVC less than 0.70 and less than the LLN thresholds using a nonparametric approach,2 and they concluded that their results support the use of an FEV1:FVC less than 0.70 to identify individuals at risk of clinically significant COPD. We have some concerns regarding the statistical methods used.
Han X, Zhang Y. FEV1:FVC Thresholds for Defining Chronic Obstructive Pulmonary Disease. JAMA. 2019;322(16):1611. doi:https://doi.org/10.1001/jama.2019.13957
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