RESUMEN
BACKGROUND: The rapid diagnosis of tuberculosis (TB) by detecting and identifying Mycobacterium tuberculosis complex (MTC) in clinical culture isolates can be achieved by a combination of rapid tests. OBJECTIVE: To propose a cost-effective laboratory protocol for MTC identification. DESIGN: MTC (n = 278) was identified using microscopic morphology, two immunochromatographic assays (ICAs) (Tibilia™ and MeDiPro(®) M. tuberculosis Antigen Rapid Test) and the strand displacement amplification (SDA) method (ProbeTec), and the results were compared. RESULTS: Microscopic morphology (cord-like) had a sensitivity of 99.3%, a specificity of 84.3%, a positive predictive value (PPV) of 88.2% and a negative predictive value (NPV) of 99.1%. The overall sensitivity/specificity of the Tibilia, MeDiPro and ProbeTec assays were respectively 98.7%/98.4%, 88.0%/85.2% and 97.4%/98.4%. The PPV/NPV for Tibilia, MeDiPro and ProbeTec were respectively 98.7%/98.4%, 87.4%/85.8% and 98.7%/96.8%. Cord-like microscopy was the least expensive method and could be used for the identification of MTC. ICA offers cost-effective screening compared to the SDA method. Tibilia performed better than MeDiPro, while its diagnostic value was similar to the SDA method. CONCLUSION: We recommend a combination of microscopic morphology and Tibilia to further improve the sensitivity and PPV of MTC identification at lower cost.
Asunto(s)
Cromatografía de Afinidad/métodos , Microscopía/métodos , Mycobacterium tuberculosis/aislamiento & purificación , Técnicas de Amplificación de Ácido Nucleico/métodos , Tuberculosis/diagnóstico , Cromatografía de Afinidad/economía , Análisis Costo-Beneficio , Humanos , Microscopía/economía , Técnicas de Amplificación de Ácido Nucleico/economía , Valor Predictivo de las Pruebas , Estudios Prospectivos , Sensibilidad y Especificidad , Tuberculosis/microbiologíaRESUMEN
The cost-effectiveness of the ProbeTec ET Direct TB assay (DTB) was compared with that of culture for detection of Mycobacterium tuberculosis complex in 361 acid-fast stain-positive respiratory specimens. The overall sensitivity, specificity, positive predictive value and negative predictive value of DTB were 97.7%, 86.6%, 87.2% and 97.6%, respectively. When clinical evaluation was added to DTB, the specificity and positive predictive value of DTB increased to 94.7% and 95.4%, respectively. Treatment costs of $133,521 would have been saved in this cohort if DTB, instead of culture results, had been used to eliminate 'false-positive' smear results.