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Susan E. Dorman, Coming-of-Age of Nucleic Acid Amplification Tests for the Diagnosis of Tuberculosis, Clinical Infectious Diseases, Volume 49, Issue 1, 1 July 2009, Pages 55–57, https://doi.org/10.1086/599038
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Until recently, a laboratory-based diagnosis of pulmonary tuberculosis (TB) has relied on the use of specimens obtained from the respiratory tract of patients; these specimens were tested by use of both smear microscopy (for visualization of stained acid-fast bacilli [AFB]) and mycobacterial culture. This approach has several limitations that have clinical implications. First, although smear microscopy is rapid, its sensitivity is relatively low (∼70% for culture-confirmed pulmonary TB, according to a recent systematic review [1], and lower still in many TB program settings). Moreover, smear microscopy cannot reliably distinguish Mycobacterium tuberculosis from nontuberculous mycobacteria, and therefore its positive predictive value is suboptimal in settings (including those in the United States) in which nontuberculous mycobacteria are commonly isolated from respiratory secretions. Mycobacterial culture is sensitive and, when combined with biochemical or molecular species identification methods, specific for TB. However, the use of culture is technically challenging and slow (i.e., it can take up to 6–8 weeks for M. tuberculosis to grow on culture).
