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

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%) were respiratory and 54 (24%) extra-respiratory specimens. The sensitivity was 88%) and 50%>, respectively, specificity and PPV was 100%> in both cases. NPV was 99.4%> in respiratory specimens and 96.1% 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.