Performance of IS6110-LAMP assay for detection of Mycobacterium tuberculosis complex in blood and urine samples from patients with extrapulmonary tuberculosis.

Background: The diagnosis of extrapulmonary tuberculosis (EPTB) shows numerous difficulties because of non-specific symptomatology and low sensitivity of conventional methods. Loop-mediated isothermal amplification (LAMP) is a fast and low-cost technique, which can amplify under isothermal conditions an amount of target DNA copies into approximately a billion copies.

Objective: The present study aimed to evaluate a IS6110-LAMP system for Mycobacterium tuberculosis detection in blood and urine samples from patients with EPTB.

Methods: The collected samples (n = 122) were stratified in two groups: Group EPTB - patient samples with confirmed EPTB (n = 61); Group non-TB - patient samples without TB (n = 61). The urine samples underwent decontamination, and the components of blood samples were separated (plasma and PBMC). DNA extractions were performed in all biological samples followed by IS6110-LAMP assay technique. The detection limit was evaluated through dilution curves (1:10) using Mtb reference strain (H37Rv) genomic DNA.

Findings: The detection limit of IS6110-LAMP was 10 fg/μL (∼10-20 bacilli/μL). The IS6110-LAMP technique sensitivity and specificity were 95.65 % and 79.25 %, respectively, with a general kappa agreement index of 0.762.

Main Conclusions: Based on these results, IS6110-LAMP test showed considerable diagnostic parameters, being able to aid in the speed and accuracy of the final EPTB diagnosis.