Role of C-reactive protein, neutrophil-to-lymphocyte ratio, and platelet-to-lymphocyte ratio as inflammatory biomarkers in chronic obstructive pulmonary disease exacerbation

Abstract

Background
Chronic obstructive pulmonary disease (COPD) is a heterogeneous respiratory condition characterized by persistent airflow limitation resulting from airway and alveolar abnormalities. Acute exacerbations represent clinically heterogeneous events frequently driven by heightened systemic inflammation, yet accessible biomarkers for timely detection remain limited in routine practice. This study aimed to evaluate C-reactive protein (CRP), neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR) as inflammatory biomarkers for identifying acute exacerbations and assessing disease severity.


Results

This single centered cross-sectional observational study enrolled 100 participants, 50 with stable COPD and 50 with acute exacerbation at Abassia Chest Diseases Hospital, Cairo, Egypt. Groups were comparable in age, sex distribution, body mass index (BMI), and smoking status. Patients with acute exacerbation exhibited significantly worse airflow limitation (mean forced expiratory volume in the first second [FEV
1
] 36.9% vs. 71.0% predicted;
p
 < 0.001) and greater physiological derangement on arterial blood gas (ABG) analysis. All systemic inflammatory markers were markedly elevated during exacerbation: CRP (60.9 vs. 5.6 mg/L), NLR (9.64 vs.2.04), and PLR (231.8 vs. 124.0) (all
p
 ≤ 0.001). FEV
1
demonstrated significant inverse correlations with CRP (
r
 = − 0.751), NLR (
r
 = − 0.617), and PLR (
r
 = − 0.283). Receiver operating characteristic analysis revealed excellent diagnostic performance for NLR (area under the curve [AUC] 0.997; cut-off 3.3; sensitivity 98%, specificity 90%) and CRP (AUC 1.000; cut-off 40.95 mg/L; sensitivity 92%, specificity 100%), while PLR showed moderate accuracy (AUC 0.840; cut-off 112.75; sensitivity 98%, specificity 54%).



Conclusions
Acute exacerbations of COPD are associated with marked elevations in systemic inflammatory biomarkers. NLR demonstrates fair discriminatory capacity for exacerbation detection. However, prospective multicenter studies controlling for disease severity and comorbidities are required before routine clinical implementation.