A major finding of the study is that both Paco2 and MR-ProANP were better prognostic parameters than historic markers of disease severity, including the parameter currently used to target therapy in COPD (ie, FEV1). The complexity and the heterogeneity of COPD strongly suggest the need for a composite score (such as the BMI, airflow obstruction, dyspnea, and exercise capacity [BODE] score) or a disease-specific comprehensive biomarker able to gather the different features of the disease. The fact that MR-ProANP is an independent predictor of prognosis determines its value beyond Paco2 measurement alone. Therefore, in contrast to the belief of Drs Alrajab and Uysal, MR-ProANP provides additional prognostic information for acute exacerbations of COPD. The influence of other comorbidities in MR-ProANP values might indeed integrate parameters of poor outcome performance in patients with COPD, who often suffer from several comorbidities. In this sense, the influence of comorbidities in MR-ProANP is more informative than confusing.