Serum Creatinine/Cystatin C Ratio as a Predictor of In-hospital Mortality in Patients Hospitalized with Acute Exacerbation of Chronic Obstructive Pulmonary Disease.

"Declarations Conflict of interestThe authors declare that they have no conflicts of interest for this work. Consent to ParticipateInformed consent was waived because our study was conducted solely by collecting retrospective anonymized patient data from electronic medical records, with no influence on patient treatment. Consent to PublishNot applicable. Ethical approvalThe study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The present study was approved by the Medical Ethics Committee of Wuhu Hospital of Traditional Chinese Medicine (LW 2022-10; May 13, 2022). Conflict of interest The authors declare that they have no conflicts of interest for this work."

"Funding This study was supported by the High-level Talents Project of the Wuhu Health Commission (2020-132, Zhixiang Chen, and 2021-134, Lei Zha)."

"Patients with AECOPD hospitalized at the Department of Respiratory and Critical Care Medicine of Wuhu Hospital of Traditional Chinese Medicine, China were enrolled in this retrospective observational study between January 2016 and February 2022. The primary outcome was in-hospital mortality. Diagnosis of COPD was based on the Global Initiative for Chronic Obstructive Lung Disease (GOLD 2018) criteria []. Inclusion criteria were hospitalized patients with AECOPD, defined as an acute deterioration in respiratory symptoms of sufficient severity to require admission. Exclusion criteria were as follows: (1) age < 40 years; (2) end-stage renal disease (ESRD), defined as estimated GFR < 15 mL/min/1.73 m2, or already receiving renal replacement therapy; (3) acute renal injury; (4) receiving palliative care; or (5) missing data required for the study. For patients with multiple hospital admissions during the study period, only the first admission record was used. As a retrospective analysis, the study was not registered."