Peripheral-Blood-Based PCR Assay to Identify Patients with Childhood Tuberculosis

ABSTRACT

PURPOSE: There is an urgent need for rapid and accurate diagnosis of childhood tuberculosis. Recently, developments in molecular biology have raised hopes about the possibilities of new strategies for tuberculosis diagnosis. Most of these methods have focused on the application of PCR to sputum samples from patients with suspected mycobacterial disease. We used a nested PCR to detect circuclating Mycobacterial tuberculosis DNA in blood samples from patients with suspected tuberculosis infection. We have propspectively investigated the role of blood-based PCR assay for diagnosis of childhood tuberculosis. METHODS: Our PCR assay is specific for IS6110 insertion element of the M.tuberculosis complex of organisms. We used it to test peripheral blood from 179 children with suspected tuberculosis infection. Results of the PCR assay were compared with tuberculin test and contact history with pulmonary tubercosis patients. A subgroup of 16 patients has blood samples assayed serially to track the PCR signal after treatment. RESULTS: In patients with contact history, 20 out of 30 samples (66.7%) were PCR positive. In patients with tuberculin test positive, 43 out of 78 samples (61.59%) were PCR positive. However there was no significant difference between weak (10-15mm) and strong (>15mm) tuberculin responsor groups. Negative conversion of PCR signal was observed in 14.3% (1/7) of subjects after 2 months of treatment, and 71.4% (5/7) after 3 months of treatment. Positive results of PCR was not observed after BCG vaccination. CONCLUSIONS: We conclude that peripheral-blood-based PCR detection for diagnosis of childhood tuberculosis is technically feasible approach that has a potential important role in diagnosis of childhood tuberculosis.