The association of delta neutrophil index with the prognosis of acute exacerbation of chronic obstructive pulmonary disease

Background Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) is associated with infective triggers including bacterial or viral in many cases, and pneumonia is a major contributor to hospitalization for AECOPD and has a close relationship with poor outcomes. Increased delta neutrophil index (DNI) can be useful in the detection of COPD patients with pneumonia. Methods A retrospective cohort study was performed to investigate the mortality rate of the patients who were re-admitted within 6 months after discharge from the hospital due to AECOPD with or without CAP. We analyzed the difference of cumulative survival rate according to serum DNI level and readmission duration. Results Finally, 140 AECOPD patients with community-acquired pneumonia (CAP) and 174 AECOPD patients without CAP were enrolled during 6 months, respectively. The mean age was 72.2 +/- 9.4 year-old, and 240 patients (76.4%) were male. When comparing the cumulative survival rate according to readmission duration (<= 30 vs > 30 days) and DNI level (< 3.5 vs >= 3.5%), AECOPD patients with readmission <= 30 days and DNI >= 3.5% showed the lowest cumulative survival rate compared to other groups (P < 0.001). Multivariate analysis revealed readmission duration <= 30 days (HR 7.879, 95% CI 4.554-13.632, P < 0.001); and serum DNI level (HR 1.086, 95% CI 1.043-1.131, P < 0.001) were significantly associated with the mortality of AECOPD patients during 6 months. The area under the curve for readmission (<= 30 days) + DNI level (>= 3.5%) was 0.753 (95% CI 0.676-0.830, P < 0.001) with a sensitivity of 73.7% and a specificity of 67.3%. Conclusion AECOPD patients who were readmitted <= 30 days and DNI >= 3.5% showed higher mortality. DNI level can be used as a predictor of prognosis in AECOPD patients who were readmitted after discharge.