Expression and clinical significance of serum C-reactive protein and blood lactate levels in elderly patients with chronic obstructive pulmonary disease complicated by acute lower respiratory tract infection.

OBJECTIVE: To evaluate serum C-reactive protein (CRP) and blood lactate levels in elderly patients with Chronic Obstructive Pulmonary Disease (COPD) complicated by acute lower respiratory tract infection (ALRTI). METHODS: A total of 265 elderly COPD patients (age ≥ 65 years) were retrospectively analyzed. According to the presence of ALRTI, patients were divided into an ALRTI group (n = 160) and a non-ALRTI group (n = 105). Serum CRP and blood lactate levels were measured within 24 hours of admission. RESULTS: Compared with the non-ALRTI group, the serum CRP and lactate levels were significantly higher in the ALRTI group (both P < 0.01). Elevated CRP (OR = 3.22) and blood lactate (OR = 2.78) were independent risk factors for ALRTI. Both markers were positively correlated with Confusion, Urea, Respiratory rate, Blood pressure, Age ≥ 65 years (CURB-65) score (r = 0.452 and r = 0.387, both P < 0.001). The area under the receiver operating characteristic (ROC) curve (AUC) for the combination of CRP and lactate in predicting intensive care unit (ICU) admission was 0.835 [95% confidence interval (CI): 0.782-0.888], which was superior to either marker alone. CONCLUSION: Serum CRP and lactate levels are significantly elevated in elderly COPD patients complicated with ALRTI and are associated with disease severity. Their combined detection may improve the identification of high-risk patients and prediction of ICU admission.