AFB = acid-fast bacilli; High TB incidence = > 100 cases per 100,000 people based on WHO estimates from 2012; HIV = human immunodeficiency virus; K = the number of studies; NAAT = nucleic acid amplification testing; TB = tuberculosis
HIV-positive patients with pulmonary TB commonly produce AFB-negative sputum specimens (de Albuquerque et al. 2014; Scherer et al. 2011). Thus, the difficulty associated with diagnosis of TB in HIV-positive patients is related to the reduced sensitivity of NAAT compared with culture in AFB-negative specimens. Figure 27 shows that 33% (1 – sensitivity) of AFB-negative sputum specimens will have a false-negative NAAT result when compared with culture; in contrast, only 3% of AFB-positive specimens will have a false-negative result. The difference in the pooled sensitivity for non-sputum specimens is more modest (14% and 0%, respectively) but still sufficient to be of some concern to clinicians.
Figure 27 Forest plot comparing the pooled sensitivity and specificity values for NAAT versus culture according to AFB result and specimen type in HIV-positive specimens
AFB = acid-fast bacilli; K = the number of studies
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