An assessment of nucleic acid amplification testing for active mycobacterial infection

Green plots represent median (range) in groups for which meta-analysis could not be conducted.

Incidence of TB based on WHO estimates from 2012: high incidence = > 100 cases per 100,000 people; medium incidence = 10–100 cases per 100,000 people; low incidence = ≤ 10 cases per 100,000 people

Figure 20 LR scattergram for diagnosis of MTB infection by NAAT compared with culture for AFB-positive specimens according to NAAT methodology

LR = likelihood ratio; NAAT = nucleic acid amplification testing

The SROC curve for studies investigating NAAT compared with culture in AFB-positive specimens showed no threshold effects based on commercial or in-house NAAT (Figure 22) or specimen type (not shown). However, for studies investigating NAAT compared with culture in AFB-negative specimens, a threshold effect was seen (Figure 23). In-house NAAT tended to be more sensitive and less specific than commercial NAAT when compared with culture. Similarly, NAAT compared with culture tended to be less sensitive and more specific when testing sputum specimens than for non-sputum specimens. The AUC for NAAT versus culture in AFB-positive (0.98; 95%CI 0.96, 0.99) and AFB-negative (0.93; 95%CI 0.91, 0.95) specimens indicated that the NAATs perform well in predicting culture positivity (AUC > 0.9) for both types of specimen.

Figure 21 LR scattergram for diagnosis of MTB infection by NAAT compared with culture for AFB-negative specimens according to NAAT methodology