Análisis retrospectivo del rendimiento de Amplicor-PCR® para la detección de Mycobacterium tuberculosis en muestras respiratorias y no respiratorias con baciloscopia negativa: A retrospective analysis / Assessment of the Amplicor PCR® for the detection of Mycobacterium tuberculosis in smear negative respiratory and non respiratory specimens

Background: Commercial polymerase chain reaction (PCR) kits are widely accepted for analysis of smear positive respiratory specimens, but the sensitivity is variable for smear negative ones. Objective: To assess the PCR method usefulness in smear negative respiratory and non respiratory specimens. Methods: We compared the PCR results (AMPLICOR MTB test™, Roche) of 235 specimens subjected to culture in Loewenstein-Jensen agar (as the gold standard). Results: 181 (76 percent) were respiratory and 54 (24 percent) extra-respiratory specimens. The sensitivity was 88 percent) and 50 percent>, respectively, specificity and PPV was 100 percent> in both cases. NPV was 99.4 percent> in respiratory specimens and 96.1 percent in non-respiratory specimens. Conclusions: The good performance of this PCR in smear negative respiratory specimens allows the clinician to take decisions based on the result of this exam. In extra-respiratory specimens the contribution is important only when the PCR result is positive.