An assessment of nucleic acid amplification testing for active mycobacterial infection

Component	A Excellent	B Good	C Satisfactory
D Poor
Evidence-base^a	One or more level I studies with a low risk of bias or several level II studies with a low risk of bias
Consistency		Most studies consistent and inconsistency may be explained
Clinical impact		Substantial
Generalisability		Population(s) studied in the body of evidence are similar to target population
Applicability		Applicable to Australian healthcare context with few caveats

^a Level of evidence determined from the NHMRC evidence hierarchy (see Table ).

Source: Adapted from NHMRC (2009)

The proportion of patients diagnosed with culture-positive MTB varied greatly among studies. In the 68 studies that compared the diagnostic accuracy of AFB microscopy and NAAT with culture in patients suspected of having TB, the proportion of patients from whom MTB could be cultured ranged from 1% to 81%, with a mean of 30%. The mean proportion of patients with culture-positive MTB infections was greater in countries with a high incidence of TB (> 100 cases per 100,000 people; 33%) than in those with intermediate (100–10 cases per 100,000 people; 29%) or low incidence (< 10 cases per 100,000 people; 24%) rates. As expected, the mean proportion of culture-positive specimens was greater in patients with AFB-positive specimens (80%, range 27–100%) than in AFB-negative specimens (19%, range 1–72%). The proportion of culture-positive specimens identified for all subgroups are listed in Table (Appendix ).