RESUMEN
In areas of low tuberculosis (TB) prevalence, laboratory diagnosis of TB may essentially cover non-tuberculous mycobacteria (NTM) in addition to Mycobacterium tuberculosis (MTB). In this study, a semi-automated PCR workflow distinguishing MTB and NTM (Anyplex™ MTB/NTMe, Seegene) and subsequently detecting MTB isoniazid/rifampicin resistance (Allplex™ MTB/MDRe, Seegene) was evaluated for replacing smear microscopy of acid-fast bacilli as the rapid screening method for TB. With 279 clinical samples, 47 cultures positive for MTB and 76 for NTM, the Anyplex™ MTB/NTMe assay and smear microscopy showed equal sensitivities (49.6% vs 50.8%, respectively) but Anyplex™ MTB/NTMe was more sensitive for MTB (63.8% vs 25.6%) than for NTM (40.8% vs 64.5%). Allplex™ MTB/MDRe showed a slightly higher sensitivity of 68.1% for MTB (32/47 positive, n = 222). Antibiotic resistance profiles were correctly identified for all MTB isolates (one MDR isolate). Specificity was 100% for both assays. Anyplex™ MTB/NTMe detected all the 18 NTM species present in the study. The analytical performance of the evaluated high-throughput workflow was relatively weak compared to culture but potentially adequate as a rapid screening method analogous to smear microscopy with additional differentiation between TB, MDR-TB, and NTM.
Asunto(s)
Automatización de Laboratorios , Farmacorresistencia Bacteriana Múltiple , Mycobacterium tuberculosis/aislamiento & purificación , Micobacterias no Tuberculosas/aislamiento & purificación , Tuberculosis Resistente a Múltiples Medicamentos/diagnóstico , Técnicas Bacteriológicas , Humanos , Técnicas de Diagnóstico Molecular , Mycobacterium tuberculosis/genética , Micobacterias no Tuberculosas/genética , Valor Predictivo de las Pruebas , Reacción en Cadena en Tiempo Real de la Polimerasa , Sensibilidad y EspecificidadRESUMEN
Today, there are numerous different molecular diagnostic assays for the detection of tuberculosis (TB), allowing the optimization of rapid detection of TB according to the clinical need. In this study, two high-throughput TB PCR assays with combined antimicrobial resistance detection, Anyplex™ II MTB/MDR (Seegene) and RealTime MTB + RealTime MTB RIF/INH Resistance (Abbott Molecular), were evaluated for routine use in a clinical setting of low population and low TB prevalence in Finland. The RealTime MTB assay was 100% concordant (22/22 positive, n = 169) with the reference methods (culture and Xpert MTB/RIF PCR assay, Cepheid). However, with a limitation of four separate PCR cycles per kit, the routine use in a low TB-prevalence setting would easily lead to wasting most of the RIF/INH Resistance reagents. The Anyplex™ II MTB/MDR assay usability was more adaptive to suit the clinical setting but the assay sensitivity was considerably lower (86%, 19/22 positive, n = 76) being closer to the sensitivity of smear microscopy. The findings of this study suggest that the evaluated high-throughput MTB/MDR assays are evidently suboptimal for routine use in a low population, low TB-prevalence setting. In addition, neither of the two assays covers non-tuberculous mycobacteria and could therefore not fully replace acid-fast staining as the initial screening method.
