[Usefulness of detecting Mycobacterium tuberculosis by genome amplification in the diagnosis of childhood pulmonary tuberculosis].

Objective: To evaluate the polymerase chain reaction in the diagnosis of pulmonary tuberculosis in children.

Patients And Methods: 135 samples (68 sputum and 67 gastric aspirates) of 72 patients under 15 years old with suspected tuberculosis and a negative acid-fast stain were included in the study. In all the samples an acid-fast stain and culture in Lowestein-Jensen with and without piruvate were performed. Also, a specific detection of Mycobacterium tuberculosis complex (MT) was made by PCR (Amplicor-MT-Roche Diagnostic). Tuberculosis was certainly diagnosed when M. tuberculosis was isolated or clinical evidence of tuberculosis in positive-PCR cases with negative culture was achieved.

Results: Ten samples of six patients were positive culture. Four of these samples were positive PCR. In addition, two samples of two patients with negative culture were positive PCR. Both patients had a clinical diagnosis of pulmonary tuberculosis with effective anti-tuberculosis treatment, one of them had also another positive PCR and culture sample. The results of sensitivity, specificity, positive predictive value and negative predictive value by patient according to the reference methodology were 57.1, 100, 100 and 95.4%, respectively, and by sample 66.6%, 100, 100 and 96.8%, respectively. Other 15 patients presented pulmonary tuberculosis with negative PCR and culture; so the sensitivity of the culture and the PCR regarding a clinical diagnosis were 27.3% (6/22) and 18% (4/22) respectively.

Conclusion: Due to the diagnosis by culture takes a long time and the low percentage of samples of pediatric patients with positive acid-fast rain stain, the PCR would be useful in order to achieve quickly and specific diagnosis of tuberculosis in a high-prevalence population.