Systematic review: Comparison of Xpert MTB/RIF, LAMP and SAT methods for the diagnosis of pulmonary tuberculosis

Summary

Technological advances in nucleic acid amplification have led to breakthroughs in the early detection of PTB compared to traditional sputum smear tests. The sensitivity and specificity of loop-mediated isothermal amplification (LAMP), simultaneous amplification testing (SAT), and Xpert MTB/RIF for the diagnosis of pulmonary tuberculosis were evaluated. A critical review of previous studies of LAMP, SAT, and Xpert MTB/RIF for the diagnosis of pulmonary tuberculosis that used laboratory culturing as the reference method was carried out together with a meta-analysis. In 25 previous studies, the pooled sensitivity and specificity of the diagnosis of tuberculosis were 93% and 94% for LAMP, 96% and 88% for SAT, and 89% and 98% for Xpert MTB/RIF. The I² values for the pooled data were >80%, indicating significant heterogeneity. In the smear-positive subgroup analysis of LAMP, the sensitivity increased from 93% to 98% (I² = 2.6%), and specificity was 68% (I² = 38.4%). In the HIV-infected subgroup analysis of Xpert MTB/RIF, the pooled sensitivity and specificity were 79% (I² = 72.9%) and 99% (I² = 64.4%). In the HIV-negative subgroup analysis for Xpert MTB/RIF, the pooled sensitivity and specificity were 72% (I² = 49.6%) and 99% (I² = 64.5%). LAMP, SAT and Xpert MTB/RIF had comparably high levels of sensitivity and specificity for the diagnosis of tuberculosis. The diagnostic sensitivity and specificity of three methods were similar, with LAMP being highly sensitive for the diagnosis of smear-positive PTB. The cost effectiveness of LAMP and SAT make them particularly suitable tests for diagnosing PTB in developing countries.

Introduction

The purpose of this review is to assess critically the current methods used to diagnose pulmonary tuberculosis (PTB), which is a contagious bacterial (Mycobacterium tuberculosis) infection that initially involves the lungs but may spread to other vital organs. It is important to diagnose PTB rapidly and accurately, as it is vital to treat patients immediately to minimize the risk of transmission of this airborne disease to other individuals in the local community. PTB is spread from person to person through the air for example when an infected individual coughs, sneezes or spits; a person only needs to inhale a few bacteria to become infected and is second only to HIV/AIDS as the greatest killer worldwide due to a single infectious agent. It has been estimated that in 2013, 9 million people contracted the disease of which 1.5 million died. More than 2 billion people are believed to be harboring M. tuberculosis but are asymptomatic [1]. Over 95% of TB deaths occur in low- and middle-income countries, and it is among the top 5 causes of death for women aged 15–44 and is a leading killer of HIV-positive people causing about 25% of all HIV-related deaths [2]. Much research has shown that early diagnosis would greatly improve efforts to prevent the spread of this devastating disease, whose symptoms include a severe cough, chest pains, night sweats, weight loss, coughing up of sputum and blood from deep within the lungs and others.

Thus, the aim of our review was to determine the diagnostic accuracies of the various methods available today to diagnose PTB, and to discuss their relative advantages and disadvantages.