Laboratory evaluation of a lateral-flow cell for molecular detection of first-line and second-line anti-tuberculosis drug resistance.

Despite the WHO9s call for universal drug susceptibility testing for all patients being evaluated for tuberculosis (TB), a lack of rapid diagnostic tests which can fully describe TB resistant patterns is a major challenge in ensuring that all persons diagnosed with drug-resistant TB are started on an appropriate treatment regime. We evaluated the accuracy of Akonni Biosystems XDR-TB TruArray® and Lateral Flow Cell (XDR-LFC), a novel multiplex assay to simultaneously detect mutations across seven genes that confer resistance to both first and second-line anti-TB drugs. The XDR-LFC includes 271 discrete three-dimensional gel elements with target-specific probes for identifying mutations in katG, inhA promoter, and ahpC promoter (isoniazid); rpoB (rifampin); gyrA (fluoroquinolones); rrs and eis promoter (kanamycin) and; rrs (capreomycin and amikacin). We evaluated XDR-LFC performance with 87 phenotypically and genotypically characterized clinical Mycobacterium tuberculosis (Mtb) isolates. Overall assay accuracy for mutation detection in specific genes was 98.6% for eis promoter and 100.0% for the genes katG, inhA promoter, ahpC promoter, rpoB, gyrA, and rrs. The sensitivity and specificity against phenotypic reference was 100% and 100% for isoniazid, 98.4% and 50% for rifampin (specificity increased to 100% once the strains with documented “low-level resistance mutations” in rpoB were excluded), 96.2% and 100% for fluoroquinolones, 92.6% and 100% for kanamycin, 93.9% and 97.4% for capreomycin and 80% and 100% for amikacin. The XDR-LFC solution appears to be a promising new tool for accurate detection of resistance to both first and second-line anti-TB drugs.