Monocyte-to-Lymphocyte Ratio (MLR) as a Possible Prognostic Marker of Latent Tuberculosis (LTBI) among Household Contacts of Active Tuberculosis (TB) PatientsTuberculosis (TB) is endemic in many developing countries including Pakistan. It is a leading cau

TB is endemic in many low socio-economic countries including Pakistan and is the leading cause of death from a single infectious agent worldwide. Identification and early treatment of latent conditions will help in reducing the burden of TB. However, identification of those with latent infection is time taking and expensive.  A potential cheap and early biomarker for this purpose may be the “Monocyte to lymphocyte ratio” (MLR). The MLR may indicate an immune response to the presence of mycobacterium tuberculosis. Since household contacts of tuberculosis patients are at increased risk of LTBI, checking correlation of their MLR to the established diagnostic investigations might help establish this simple test as an extremely useful biomarker for LTBI. A cross sectional study was designed to find the efficacy of monocytes to lymphocytes ratio in identifying latent tuberculosis among household contacts of patients with active tuberculosis. About 40 patients recently diagnosed with active tuberculosis and 40 close contacts of these patients and 20 controls were included in the study Mean ratio of monocytes to lymphocytes was 0.165 in patients with active tuberculosis and 0.06 (range 0.03–0.08) in close contacts of patients and 0.04 (0.02–0.04) in controls. Ratio of monocytes to lymphocytes (> 06 %) were significant predictors for latent tuberculosis. It is an additional observation that patients with pulmonary tuberculosis with an age of greater than 50 years were seen to have higher ratio of monocytes to lymphocytes. Ratio of monocytes to lymphocytes (> 0.06) may help in diagnosing latent tuberculosis in close contacts of tuberculosis patients. Copyright(c) The Authors