An assessment of nucleic acid amplification testing for active mycobacterial infection

Comparison of NAAT and culture, using clinical diagnosis as a reference standard

In order to compare the sensitivity and specificity of culture and NAAT, using clinical diagnosis as a reference standard, meta-analysis was conducted using data from 10 of the included studies that provided data using a clinical reference standard. The basis for a positive clinical diagnosis differed between studies but included some or all of the following: clinical findings, AFB microscopy, histology/cytology, chest radiographic findings, site-specific CT scan / MRI results, culture results and response to anti-TB drug therapy. The pooled sensitivity for culture versus clinical diagnosis was 76% (95%CI 54, 90) compared with 86% (95%CI 77, 92) for NAAT versus clinical diagnosis (Figure ). This indicated that 24% of patients clinically diagnosed with TB will have a false-negative culture result compared with 14% having a false-negative NAAT (1 – sensitivity). This finding was consistent with the proportion of culture-positive cases reported in the Tuberculosis notifications in Australia, 2010 Annual Report¹⁰; 78% of all MTB cases were confirmed by culture.

Figure Forest plot showing the pooled sensitivity and specificity values for culture compared with NAAT, using a clinical reference standard, and for NAAT compared with culture in the same subset of studies

CRS = clinical reference standard; K = the number of studies; NAAT = nucleic acid amplification testing