RESUMO
OBJECTIVE: To study the value of a rapid diagnostic method based on the amplification by polymerase chain reaction (PCR) of a fragment of the IS6110 insertion element for the detection of Mycobacterium tuberculosis in children. DESIGN: We tested 199 specimens obtained from 68 children referred for evaluation of suspected tuberculosis. RESULTS: In 83.3% of children with active disease and 38.9% with tuberculous infection but no evidence of disease, at least one positive PCR result was observed. No child without tuberculosis had positive PCR results (100% specificity). The sensitivity of the PCR was increased by testing of multiple samples from the same child and use of Chelex particles (Bio-Rad Laboratories, Ivry, France) rather than guanidine isothiocyanate-silica particles for DNA extraction. Bronchoalveolar lavage samples were no more useful than gastric aspirates. CONCLUSIONS: If appropriate laboratory methods are used, DNA amplification is a reliable method for the early diagnosis of tuberculosis in children and appears to be very helpful in clinical pediatric practice when the diagnosis of active tuberculosis is difficult or needs to be rapidly confirmed.