The polymerase chain reaction (PCR) and its variations, such as the nested-PCR, have been described as
promising techniques for rapid diagnosis of tuberculosis (TB). With the aim of evaluating the usefulness of a
nested-PCR method on samples of blood and urine of patients suspected of tuberculosis we analyzed 192
clinical samples, using as a molecular target the insertion element IS6110 specific of M. tuberculosis
genome. Nested-PCR method showed higher sensitivity in patients with extrapulmonary tuberculosis (47.8%
and 52% in blood and urine) when compared to patients with the pulmonary form of the disease (sensitivity
of 29% and 26.9% in blood and urine), regardless of the type of biological sample used. The nested-PCR is a
rapid technique that, even if not showing a good sensitivity, should be considered as a helpful tool especially
in the extrapulmonary cases or in cases where confirmatory diagnosis is quite difficult to be achieved by
routine methods. The performance of PCR-based techniques should be considered and tested in future works
on other types of biological specimens besides sputum, like blood and urine, readily obtainable in most
cases. The improving of M. tuberculosis nested-PCR detection in TB affected patients will give the
possibility of an earlier detection of bacilli thus interrupting the transmission chain of the disease.
