Smear microscopy as a diagnostic tool of tuberculosis: Review of smear negative cases, frequency, risk factors, and prevention criteria

Tuberculosis is one of the global health problems, the estimated deaths due to TB was around 2 million in the year 2013. Failure in early diagnosis and providing suitable treatment leads to increase the prognosis of the disease. Smear microscopy is used in many countries as a primary diagnosis of TB especially in the district poor facility laboratories, where smear negative frequency is high. This review aimed to reflects the importance of smear negative tuberculosis as a source of infection and poor prognosis of TB treatment and prevention. In addition to, discuss the possible causes and suggests solutions to improve the yields of smear microscopy.