Diagnostic accuracy of Xpert MTB/RIF versus smear microscopy in the early diagnosis of tuberculosis in the real life of the “Umberto I” Hospital in Rome

Tuberculosis (TB) is an important and potentially fatal infection in humans, and it is estimated that one-third of the world’s population is infected by Mycobacterium tuberculosis, with the majority suffering from a latent form of infection (WHO, 2015). Despite lower TB mortality rates in high income countries, the early diagnosis and subsequent treatment of individuals with active TB remains essential to control the spread of the disease and is an important step for TB control programmes worldwide. Smear microscopy is the most commonly used method with rapid results, identifies acid fast bacilli (AFB) not M. tuberculosis, which may affect its specificity in settings with a low burden of TB or places with a high prevalence of non-tuberculosis mycobacteria (NTM). Smear microscopy has limited sensitivity, which is further reduced in HIV-positive individuals. In addition it cannot distinguish between viable and non-viable organisms and cannot provide information on drug resistance, an understanding of which is critical for TB control (Siddiqi et al., 2003; Steingart et al., 2006). Conventional mycobacterial culture (either solid or liquid), considered the gold standard for diagnosing of TB, is prone to contamination, the results are inevitably delayed due to the slow growth of mycobacteria, and in general require the use laboratories with appropriate biosafety infrastructure (Muyoyeta et al., 2009). The development of the Xpert MTB/RIF assay (Cepheid, Sunnyvale, CA, USA) has been considered an important breakthrough in the fight against TB. Xpert MTB/RIF de-