Evaluation of loop-mediated isothermal amplification as a point-of-care diagnostic tool for mycobacterium tuberculosis

Abstract

Background: The bacterium Mycobacterium tuberculosis is the causative agent of tuberculosis. According to the World Health Organization (WHO), there were an estimated 8.8 million incident cases of tuberculosis globally in 2010. Kenya is on the list of 22 high-burden TB countries in the world and has the fifth highest burden in Africa. The loop-mediated isothermal amplification (LAMP) technique has the potential to serve as a simple, rapid, specific and costeffective point-of-care diagnostic tool. Broad Objective: To evaluate the performance of LAMP against culture on Lowenstein-Jensen for diagnosis of tuberculosis. Study Design: This study was a cross-sectional study. LAMP assay was evaluated against culture on LJ for the diagnosis of tuberculosis. Methodology: Culture on LJ medium was conducted at the National Tuberculosis Reference Laboratory. LAMP assay was conducted at UNITID. A set of 6 primers, comprising 2 outer primers (F3 and B3), 2 inner primers (FIP and BIP), and 2 loop primers (FLP and BLP), were used. LAMP amplicons in the reaction tube were detected under UV light after adding 1.0 μl of 1/10-diluted original SYBR Green I to the tube and observed the color of the solution. The solution fluoresced green in the presence of a LAMP amplicon, while it remained orange with no amplification. Results: The study showed a sensitivity of 98.6%. This means that 98.6% of the study population was declared to be diseased and 1.4% of the population was falsely declared to be disease-free by the test. The study showed a specificity of 96.4%, which means that 96.4% of the study population was declared to be disease-free, while 3.6% was falsely declared to be diseased by LAMP. Conclusion: Due to its ease of use in developing countries and its high sensitivity and specificity, this assay may be adopted to facilitate the identification of M. tuberculosis without the use of culture.