Rapid detection of Mycobacterium tuberculosis complex by real-time PCR in sputum samples and its use in the routine diagnosis in a reference laboratory.

Abstract

Tuberculosis (TB) is an infectious disease of global distribution, constituting a serious public health problem in Brazil. São Paulo State, located in the south-east of Brazil, notified 16,580 new TB cases in 2013. The Instituto Adolfo Lutz is a public health reference laboratory for TB diagnosis for all the State. Considering that rapid and accurate diagnosis is essential for TB control, the aim of this study was to evaluate the use of an in-house real-time (RT)-PCR assay targeting the mpt64 gene in the routine diagnosis of TB, and to compare this technique with smear microscopy and culture. From August 2012 to October 2013, 715 sputum samples from 657 patients were included in the study. Smear microscopy, culture, phenotypic and PRA-hsp65 identification of mycobacteria, and mpt64 RT-PCR were performed. With respect to confirmed TB cases (n = 62/657; 9.4%), smear microscopy had a sensitivity of 82.3%. Culture and RT-PCR showed the same sensitivity, i.e. 90.3%. Specificity was 99.7, 99.4 and 98.6% for smear microscopy, culture and RT-PCR, respectively. mpt64 RT-PCR showed high sensitivity and specificity for the detection of Mycobacterium tuberculosis complex in sputum samples. This technique can be deployed in laboratories that do not have a rapid test for TB available, enabling the performance of TB diagnosis in up to 5 h.