The Mycobacterium tuberculosis (M. tb) infection is largely spread in world's population. Most infected individuals develop latent tuberculosis infection (LTBI). Tuberculin skin test (TST) and interferon-gamma release assays (IGRAs) are the available tests to detect the infection. It has been reported that some individuals take a longer period of time to develop the infection than others with the same exposure level. It is suggested that the innate immunity, in which neutrophils have an important protective role, is responsible for this. Many hematologic abnormalities have been described as common findings during severe disease. To investigate if these changes are related to LTBI development and if they interfere in TST and IFN-γ production, we recruited 88 household contacts of tuberculosis (TB) pulmonary patients and compared blood cell counts with these tests' results. There were no statistically significant changes in hemoglobin, hematocrit, platelets, global leukocyte, neutrophils, basophils, eosinophils, typical lymphocytes, atypical lymphocytes, and monocytes counts between infected and noninfected individuals. Also, there was no correlation between TST or IGRA and blood cell counts. These results suggest that blood cell counts are not LTBI markers and do not interfere in TST results or IFN-γ levels obtained by IGRA. 1. Introduction Tuberculosis (TB) continues to be a public health problem worldwide. The disease is one of the most important causes of death from infectious diseases, and the infection with Mycobacterium tuberculosis (M. tb) is also disseminated throughout world’s population [1]. Brazil has notified the highest number of TB cases in America for the last 10 years. In 2010, there were estimated 85,000 new cases of TB, and approximately 6,700 of them occurred in Bahia state [1, 2]. The transmission occurs by inhalation of droplets containing the bacilli from pulmonary TB individuals, mainly for their household contacts (HHCs) who are the most exposed to the infection. Only 5%–10% of infected individuals develop active TB, and the remaining individuals will develop latent tuberculosis infection (LTBI). The latency represents a balance between intracellular bacilli survival and host defense [3]. However, considering that the reactivation of latent infection is related to a high percentage of cases and significantly increases the transmission, diagnosing and treating people with LTBI is crucial to control the disease worldwide [4]. The most common test to detect LTBI is the tuberculin skin test (TST) that basically consists in measuring
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