Microscopic smears of body fluids remain an essential part of TB

Microscopic smears of body fluids remain an essential part of TB diagnosis. Results should be available within 1 working day. Identification of mycobacteria is performed at reference centres, and is based on morphology, growth and biochemical characteristics. M. tuberculosis needs to be distinguished from other mycobacteria, for which treatment may be different and there are no infection-control

concerns. Cultures are central to the confirmation and identification of the mycobacterium, and for drug susceptibility testing. More rapid results are obtained from liquid media, which usually grow M. tuberculosis in 7–28 days. Drug susceptibility tests are usually available within 10–21 days of the laboratory receipt of HIF inhibitor isolates and are performed using standard assays. When

it is important to differentiate rapidly, gene probes are increasingly used in some laboratories, but are less sensitive than culture and are used mainly on respiratory specimens. Most nucleic acid amplification methods to detect M. tuberculosis are complex, labour-intensive, and technically challenging. The sensitivity and specificity estimates of commercial nucleic acid amplification tests (NAATs) are highly variable, compared with culture [12,13]. All specimens, even those negative for M. tuberculosis on polymerase chain reaction 5-Fluoracil clinical trial (PCR), still require culture because a negative PCR does not exclude TB and a positive PCR does not indicate the drug susceptibility profile [14,15]. However, recently a fully automated molecular test for TB identification and drug resistance testing has been evaluated on sputum samples from adult patients with TB or MDR-TB [16]. The Xpert MTB/RIF (Cepheid, Sunnyvale, CA, USA), an automated molecular test for M. tuberculosis identification and resistance to rifampin, uses a hemi-nested real-time PCR assay. This assay identifies >97% of all patients with culture-confirmed TB, including >90% of patients

with smear-negative disease. The result can be available in hours. The assay has been developed as a laboratory-based and point-of-care test for developing countries, but may be useful in rapid diagnosis of TB in the United Kingdom. Currently there are no data derived from children Abiraterone supplier or using nonrespiratory specimens in HIV-infected persons. Molecular tests for rifampicin resistance are useful especially when MDR-TB is suspected, as about 95% of isolates that are rifampicin resistant will also be isoniazid resistant. As MDR-TB is defined as TB resistant to at least rifampicin and isoniazid, patients with positive molecular-based rifampicin resistance should be treated as having MDR-TB until the full resistance profile from cultures is available. Tuberculin testing can identify patients with latent infection but there are high false-negative rates in HIV-positive patients, especially in those with low CD4 cell counts [17–23].

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