MOLECULAR DIAGNOSIS OF TUBERCULOSIS

Rapid and sensitive tools for the diagnosis of tuberculosis are needed , due to the increased incidence of tuberculosis epidemics and the len gth of time required by classical diagnostic tests, especially among h uman immunodeficiency virus (HIV)-infected patients. In this context, the recent advances in cloning and characterization of M, tuberculosis genes has allowed the application of basic molecular biology techniqu es to the examination of clinical samples, such as sputum and bronchoa lveolar lavage (BAL), for the molecular diagnosis of tuberculous infec tion, By using the polymerase chain reaction (PCR) for the amplificati on of mycobacterial nucleic acids and nonradiometric revelation techni ques, the time required for the identification of mycobacteria has bee n considerably shortened (24-48 h), in comparison to the time required by microbiological tests, When PCR technique is performed by experien ced laboratory personnel using controlled protocols, false-negative (c aused primarily by endogenous polymerase inhibitors) and false-positiv e results (due to contamination) can generally be avoided, achieving s ensitivity and specificity close to 100%. In the clinical practice, th e use of molecular testing for the diagnosis of tuberculosis, in combi nation with ''classic'' diagnostic tools, can greatly enhance the diag nostic ability of pulmonary clinicians, particularly in paucibacillary infections and in patients with atypical presentation, such as immuno deficient individuals.