Elevated Serum C-Reactive Protein to Lymphocyte Ratio is a Predictor of Pneumonia in Patients with Type 2 Diabetes Mellitus

Abstract

Background: Type 2 diabetes mellitus is associated with an increased risk of certain infections, such as pneumonia. Timely diagnosis and treatment of infections is crucial in populations with diabetes. The C-reactive protein to lymphocyte ratio (CLR) has been proposed as a novel marker of inflammation. We studied the role of CLR in subjects with diabetes who had pneumonia. Methods: A total of 426 subjects with pneumonia and type 2 diabetes mellitus who presented to the pulmonology clinics of Hisar Intercontinental Hospital were enrolled in the study, and 161 patients with diabetes who had no pneumonia were enrolled as controls. Overall, 176 (66.4%) of the diabetic pneumonia group and 101 (62.7%) of the control subjects were men. C-reactive protein (CRP) was analyzed using Enzyme-Linked Immunosorbent Assay (ELISA) immune assay, and lymphocytes were counted by an automatic analyzer. The CLR levels of patients with diabetes comorbid with pneumonia were compared to those diabetics without pneumonia in the present cross-sectional study. Results: Median CLR levels of the patients with diabetes comorbid with pneumonia and control subjects were 28.7 (1.1–116)% and 1.9 (0.04–12.2)%, respectively (p < 0.001). The CLR of the participants was significantly and positively correlated with their white blood cell count (r = 0.21, p < 0.001) and serum creatinine levels (r = 0.2, p < 0.001). Receiver operating characteristic (ROC) analysis revealed that CLR (when higher than 5.73%) had 86% sensitivity and 91% specificity in detecting pneumonia in patients with diabetes (AUC (area under the curve): 0.945, p < 0.001, 95% CI (confidence interval): 0.926–0.964). The sensitivity and specificity of CLR was higher than separate values of C-reactive protein (76% sensitivity and 71% specificity when higher than 7.1 mg/L; AUC: 0.813, p < 0.001, 95% CI: 0.774–0.852) and blood leukocyte count (65% sensitivity and 70% specificity when higher than 7.9 k/mm³; AUC: 0.665, p < 0.001, 95% CI: 0.614–0.716). Conclusion: These findings suggest that CLR could be a useful marker in the timely diagnosis of pneumonia in populations with diabetes.