The role of serum chloride ion in the prognosis of COPD

Background : As exacerbations of chronic obstructive pulmonary disease (COPD) are one of the leading causes of hospitalization and are associated with significant mortality, it is particularly important to accurately assess the risk of exacerbations in COPD. Most of the current clinical biomarkers are related to inflammation and few consider how ion levels affect COPD. While chloride ions, the second most abundant serum electrolyte, have been shown to be associated with poor prognosis in several diseases, but their relationship with COPD remains unclear. Methods : In total, 105 patients with acute exacerbations of COPD were recruited. Data on clinical characteristics, lung function, blood count, blood biochemistry, relevant scales including the Clinical COPD Questionnaire (CCQ), BODE (BMI, airflow obstruction, dyspnea, exercise capacity) index and the St George's Respiratory Questionnaire (SGRQ) were collected from all patients for statistical analysis. Result : There were significant differences in lung function indicators and disease severity in the low chloride ion subgroup compared with the high chloride ion subgroup. On multiple logistic regression analysis, chloride ion was an independent factor affecting lung function in COPD patients (OR= 0.823, 95% CI: 0.730 - 0.929, p=0.002). The sensitivity of chloride ion in predicting COPD severity was 78%, the specificity was 63% and the area under the curve was 0.724 (p < 0.001). Subgroup analysis showed that chloride ion was a stronger predictor in male, smoking patients. Conclusions : Chloride ion is a novel prognostic biomarker for COPD, and low levels of chloride ion are independently associated with exacerbations in COPD patients.