Molecular assays for the initial diagnosis of tuberculosis in a low-prevalence setting: A comparative study

Abstract

Introduction

The WHO's End TB Strategy promotes using rapid molecular assays as initial diagnosis to reduce tuberculosis globally. This prospective study assessed commercial molecular platforms’ effectiveness in diagnosing or ruling out tuberculosis (TB) in a low-prevalence setting.

Methods

One hundred clinical samples (80 respiratory/20 non-respiratory) were included among all samples routinely received in a mycobacterial laboratory. Five real-time polymerase-chain-reaction (RT-PCR) assays (Xpert-MTB/Rif-Ultra, BDMAX-MDR-TB, RealTime-MTB, FluoroType-MTBDR, Anyplex-MTB/NTM) were characterized and compared through blinded-parallel analysis. Sensitivity, specificity, likelihood ratios, and Cohen's Kappa were calculated to assess the accuracy and agreement of RT-PCR results with culture.

Results

Sensitivity ranged 88.89–100%, improving initial screening by 30–40%. Specificity was 96.70–98.98%. RT-PCR showed excellent discriminatory power, as TB patients were 26.9–91.0 times more likely to test positive. Cohen's Kappa showed substantial to excellent concordance (0.78–0.94).

Conclusion

RT-PCR improves TB initial diagnosis, offering tailored solutions for diverse laboratories, revolutionizing control strategies with its operational flexibility.

Resumen

Introducción

La Estrategia Fin a la Tuberculosis (TB) de la OMS impulsa ensayos moleculares rápidos como diagnóstico inicial de tuberculosis. Este estudio evaluó su eficacia en un entorno de baja prevalencia.

Métodos

Se incluyeron cien muestras clínicas (80 respiratorias/20 no respiratorias) recibidas rutinariamente en el laboratorio, analizando en paralelo 5 ensayos moleculares comerciales de RT-PCR (Xpert®-MTB/Rif-Ultra, BDMAX™-MDR-TB, RealTime-MTB, FluoroType®-MTBDR, Anyplex™-MTB/NTM). Se calcularon sensibilidad, especificidad, razones de verosimilitud y el índice kappa de Cohen para evaluar la precisión y la concordancia de los resultados de RT-PCR con el cultivo.

Resultados

La sensibilidad fue entre el 88,89-100%, mejorando el cribado inicial un 30-40%. La especificidad fue entre el 96,70-98,98%. Las RT-PCR mostraron un excelente poder discriminatorio, ya que los pacientes con tuberculosis eran 26,9-91,0 veces más propensos a dar positivo. El índice kappa Cohen mostró una concordancia de sustancial a excelente (0,78-0,94).

Conclusión

Las RT-PCR mejoran el diagnóstico inicial, ofreciendo soluciones adaptadas para diversos laboratorios, y revolucionando las estrategias de control con su flexibilidad operativa.