[Modern methods in the diagnosis of tuberculosis: PCR--polymerase chain reaction]

The diagnosis of tuberculosis depends on many factors but essentially on the detection of mycobacteria, their identification to the species level, and their susceptibility to major antituberculous drugs. The classic tests (direct examination-Ziehl-Neelsen, conventional culture and antibiotic susceptibility tests) are combined with modern tests (the molecular tests such as genomic amplification /PCR/ direct from clinical samples). By Polymerase Chain Reaction (PCR) over a billion identical bacteria could be multiplied from a single DNA molecule. These modern tests shortened diagnostics duration from several weeks to one or two days. The sensitivity of PCR test was 97% for Z-N positive, 68% for Z-N negative samples while specificity was 99% either for Z-N positive or negative samples.