Abstract
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.
Highlights
Mycobacterium tuberculosis is an acid-fast bacillus that can cause pulmonary and extra-pulmonary tuberculosis[1,2]
The most important finding of our study was that initial delta neutrophil index (DNI) values were significantly lower in patients with pulmonary tuberculosis (PTB) compared with patients with community-acquired pneumonia (CAP), and the discriminatory power of the DNI for diagnosing PTB was higher than commonly used inflammatory blood markers, such as white blood cell (WBC) or C-reactive protein (CRP), suggesting the utility of the DNI to discriminate PTB from CAP
Given that the relatively high sensitivity (89%) and negative predictive value (NPV) (95%) for diagnosing PTB at a DNI cut-off ≤ 1.0%, the initial DNI value may be useful to rule out the possibility of PTB when suspected patients have DNI values > 1.0%
Summary
Mycobacterium tuberculosis is an acid-fast bacillus that can cause pulmonary and extra-pulmonary tuberculosis[1,2]. According to the 2016 World Health Organization global report, tuberculosis was one of the top 10 causes of death worldwide, ranking above acquired immune deficiency syndrome, and there were an estimated 10.4 million newly diagnosed tuberculosis cases worldwide[3]. Because the clinical features of PTB are nonspecific or similar with those of CAP in many cases[5,6] and the diagnostic sensitivity of a microscopic examination for diagnosing tuberculosis is only about 60%, it is difficult to accurately discriminate PTB from CAP in the early stages of the diagnostic process, when managing patients with mild symptoms. No data are available regarding the clinical usefulness of the DNI for discriminating PTB from CAP. With PTB and CAP and evaluated how well the DNI value predicted PTB compared with other commonly used inflammatory blood markers
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