Accuracy of Xpert MTB/RIF assay in diagnosis of tuberculosis a comparison to culture

Abstract

Culture method is the most sensitive and specific method for the detection of Mycobacterium tuberculosis. Despite this, cultures are highly prone to contamination and the process can still take several days and does require expensive equipment, strict biosafety practices and well trained technical staff .Among the currently available Nucleic Acid Amplification Tests (NAAT), the Xpert MTB/RIF Assay (CB-NAAT), the LINE Probe Assay (LPA) and the Loop-Mediated Isothermal Amplification (LAMP) are endorsed by WHO for in vitro diagnosis of TB. The present study was carried out to assess the performance of CB-NAAT (Cepheid GeneXpert®) system for the diagnosis of MTB in both pulmonary and extra pulmonary specimens, within the demographic area of south Kashmir, India. Materials and methods: In this study Pulmonary & extra pulmonary specimens received at the Microbiology laboratory, from the new clinically suspected tuberculosis patients were used. The samples received at the laboratory were divided into three portions, one part each was used for AFB direct smear preparation, CB-NAAT and culture, respectively. A smear was reported positive if either the direct or the concentrated smear showed the presence of AFB. The concentrates were cultured on LJ media and incubated for up to 8 weeks.