Diagnosis of tuberculosis in children using a polymerase chain reaction

We investigated the value of the polymerase chain reaction (PCR) in the diagnosis of active tuberculosis in children and evaluated the relationship between PCR results in children with tuberculous infections and mediastinal adenopathies detected by computerized tomography (CT-Scan). This was a controlled, blinded, prospective study comparing nested PCR, mycobacterial cultures and the clinical diagnosis based on 350 clinical specimens from 117 children referred for evaluation of suspected pulmonary tuberculosis. All children with tuberculous infection but without active disease underwent a chest CT-scan to detect the presence of mediastinal adenopathies not evident on chest x-ray. The sensitivity of PCR was 56.8% in children with clinically active disease (culture: 37.8%; smears: 13.5%). A major advantage of PCR over cultures was noted when there was no parenchymal involvement on chest radiograph and when the patient was undergoing anti-tuberculous treatment. There were nine specimens with false-negative PCR results due to the presence of amplification reaction inhibitors. PCR was positive in five children with tuberculous infection without active disease and these children presented mediastinal adenopathies on the CT-scan that were not evident on chest radiography. There were no false-positive PCR results in the control groups of children. We conclude that nested PCR is a rapid and sensitive method for the early diagnosis of tuberculosis in children. It is especially useful when the diagnosis of active tuberculosis is difficult. In our study children with tuberculous infection without apparent disease who have positive PCR results have mediastinal adenopathies on CT-scan.