The utility of delta neutrophil index in differentiation of pulmonary tuberculosis from community acquired pneumonia

No data exist on the usefulness of the delta neutrophil index (DNI) to discriminate pulmonary tuberculosis (PTB) from community-acquired pneumonia (CAP). We performed a retrospective cohort study involving patients with PTB (n = 62) and CAP (n = 215), and compared their initial DNI levels. The median DNI values were 0% (interquartile ranges [IQR] 0–0.2%) and 1.6% (IQR 0.7–2.9%) in PTB and CAP, respectively, which was significantly lower in PTB patients (P < 0.001). Sixty-nine percent of patients with PTB had DNI value of 0%; however, only 15% of patients with CAP had 0% DNI. The discriminatory power of the DNI for diagnosing PTB was high with 89% sensitivity and 67% specificity at a DNI cut-off ≤ 1.0% (area under the curve, 0.852). The diagnostic sensitivity and negative predictive value (NPV) for PTB were 89% (55/62) and 95% (145/152) at the DNI cut-off ≤ 1.0%, respectively, and in multivariate analyses after adjusting for other factors (smoking, no fever, upper lobe involvement), DNI ≤ 1.0% remained significant (odds ratio, 15.265; P < 0.001). We demonstrated that the DNI was lower in PTB compared with CAP, and an initially elevated DNI (>1.0%) may be useful to rule out the possibility of PTB due to its high NPV.