Introduction

Globally there were an estimated 8.6 million new cases of tuberculosis (TB) in 2013 and 1.3 million deaths. India and China alone accounted for 26% and 12% of total cases, respectively.1 Community-acquired pneumonia (CAP) is one of the most important infectious causes of death. Early diagnosis and appropriate administration of antibiotics are essential for reducing pneumonia-related morbidity and mortality.2 Many studies conducted in high-tuberculosis (TB) burden countries have shown that Mycobacterium tuberculosis is a frequent cause of CAP; however, it is difficult to distinguish pulmonary TB from bacterial CAP during the initial diagnostic stage.3,4 The clinical and radiographic features of TB are often nonspecific, and the sensitivity of microscopic examination of expectorated sputum for acid-fast bacilli is as low as 50-60%.5 The incidence of TB being diagnosed among patients presenting with clinical and radiological signs of a CAP has varied across series and can be as high as 35 percent of microbiologically confirmed pneumonias, the incidence being higher in the HIV-positive subgroup of patients.6,7

Mycobacterium tuberculosis was not an uncommon cause of CAP requiring hospitalization in Malaysia. A longer duration of symptoms, history of night sweats, upper lobe involvement, cavitary infiltrates, lower total white blood cell count and lymphopenia were predictive of PTB.8 Nosocomial transmission of pulmonary TB to other hospitalized patients and healthcare workers can occur. Recently, some studies have suggested that biomarkers such as C-reactive protein (CRP), procalcitonin and soluble triggering receptor expressed on myeloid cells may play arole in discriminating pulmonary TB from bacterial CAP.9,10,11 However, not all of these biomarkers are available in countries with a high TB burden.

The neutrophil-lymphocyte count ratio (NLR) is a readily calculable laboratory marker used to evaluate systemic inflammation. The NLR obtained at the initial diagnostic stage is a useful laboratory marker to discriminate patients with pulmonary TB from patients with bacterial CAP in an intermediate TB-burden country. 2 Ratio of monocytes to lymphocytes 25% is predictive of active tuberculosis.1 Delta neutrophil index 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.12

Hence this study was planned to investigate the role of the NLR in discriminating patients with active pulmonary TB from those with bacterial CAP and compare the diagnostic ability of the NLR.

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Dr Sreenath Reddy. K

Department of General Medicine, Sri Devaraj Urs Medical College, Sri Devaraj Academy of Higher Education and Research, Tamaka, Kolar-563103, Karnataka, India