An assessment of nucleic acid amplification testing for active mycobacterial infection
Appendix E Meta-analysis of studies assessing the diagnostic accuracy of AFB compared with culture
Download 12.08 Mb.
|
Appendix E Meta-analysis of studies assessing the diagnostic accuracy of AFB compared with cultureOf the 68 studies that compared the diagnostic accuracy of AFB microscopy to culture in patients suspected of having TB, 39 performed AFB microscopy using ZN staining, 23 used fluorescent stains such as auramine, 2 used alternative stains and 3 did not report the method used. Interestingly, 18/24 (75%) studies comparing AFB microscopy and the Xpert assay used fluorescent staining, whereas 34/44 (77%) of studies using in-house NAAT methods used ZN staining. Forest plots showing the sensitivity and specificity for these studies are shown in Figure 38 and Figure 39 (Appendix D). The sensitivity varied greatly between studies, ranging from 5% to 100% with a pooled sensitivity of 62% (95%CI 54, 69). There was less variability in the specificity, which was above 80% in all but 3 studies, with a pooled value of 98% (95%CI 97, 99). The proportion of culture-positive specimens that were AFB-positive is higher in these studies than that reported in the Tuberculosis notifications in Australia, 2010 Annual Report 30, which reported that, of all MTB cases confirmed by culture, only 47% were AFB-positive. Subgroup analysis was undertaken to determine the effects of AFB methodology, specimen type, incidence of TB in the country in which the study was conducted, and use of in-house or commercial NAAT index test on the accuracy of AFB microscopy (Figure 51). There was a significant difference in sensitivity between studies investigating diagnostic accuracy in patients who provided sputum samples (71%; 95%CI 59, 81) compared with those that provided non-sputum samples (46%; 95%CI 37, 55), as the 95%CIs did not overlap. Non-sputum specimens included patients suspected of having either pulmonary TB (e.g. bronchial aspirates) or extrapulmonary TB (e.g. synovial fluid or tissue biopsy). Analysis of extrapulmonary specimens alone showed that the sensitivity and specificity of AFB compared with culture did not differ markedly from those for non-sputum samples (Table 94 in Appendix D). For some specific specimen types there were sufficient studies for separate analysis (Figure 40 in Appendix D). The pooled sensitivity for AFB microscopy compared with culture varied from 46% in urine to 62% in FNAs of lymph nodes. However, for CSF the pooled sensitivity was only 11%. Thus, AFB microscopy is not a useful tool for diagnosis of TB in CSF specimens. The pooled specificity was at least 94% in all specimen types. There was an overall 11% difference in sensitivity of AFB microscopy compared with culture, favouring studies that used an in-house NAAT over those that used the commercial Xpert NAAT, which was not statistically significant. However, this difference was entirely due to the type of specimen tested. In studies that used sputum samples, AFB microscopy was 24% more sensitive compared with culture when an in-house NAAT was used as the index test instead of a commercial NAAT. Conversely, there was no difference in sensitivity in studies that used non-sputum samples (Figure 51). The reason for this is unclear, although there is likely to be some publication bias, as indicated by the significant asymmetry when comparing the effective sample size between studies (Figure 52). This asymmetry was no longer significant (p>0.05) when the studies were separated according to AFB methodology, NAAT methodology or specimen type (data not shown). Other variables that may influence publication bias include funding, conflict of interest, prejudice against an observed association and sponsorship, but the effects of these parameters were not tested. 
Figure 51 Forest plot showing the pooled sensitivity and specificity values for AFB microscopy compared with culture for studies grouped according to NAAT comparator, AFB methodology and incidence of TB in the country in which the study was conducted Directory: internet internet -> Applications and limitations internet -> L. and Gossypium barbadense internet -> Natural Resources Conservation Service Conservation Practice Standard internet -> Practice Exercise Created By Stavros Charalambous The Internet internet -> It’s a good Topic internet -> National Preventative Health Strategy – the roadmap for action internet -> Downloading gps gr-3 Surveys Summary of Procedure internet -> 3G300m-how to setup the 3g router Mode? Product line: 3g question categories: Function configurations Note internet -> Installation Work has never been simpler or easier Download 12.08 Mb. Share with your friends:
|