Low diagnostic accuracy of Xpert MTB/RIF assay for extrapulmonary tuberculosis: A multicenter surveillance

Abstract

Diagnostic accuracy of Xpert MTB/RIF assay for pulmonary tuberculosis (PTB) and extrapulmonary TB (EPTB) has not been investigated in Iran. This study was aimed to assess the diagnostic accuracy of Xpert MTB/RIF assay for both PTB and EPTB. A total of 2111 clinical samples (1218 pulmonary and 838 extra-pulmonary) were collected from 16 medical centers during the study period and were analyzed for detection of PTB and EPTB by both Xpert MTB/RIF assay and standard conventional methods (culture and direct smear microscopy). The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of Xpert MTB/RIF assay for PTB were found to be 95.5%, 96.7%, 83.8%, and 99.1% respectively. For EPTB, the sensitivity, specificity, PPV and NPV of Xpert MTB/RIF assay counted for 76.5%, 95.9%, 62%, and 97.9% respectively. Xpert MTB/RIF assay found to be highly sensitive, specific and comparable to standard conventional methods for the diagnosis of PTB. However, the sensitivity and specificity of Xpert MTB/RIF for EPTB specimens were highly variable; thus, Xpert MTB/RIF cannot be recommended to replace standard conventional tests for diagnosis of EPTB.

Diagnostic test accuracy of Xpert MTB/RIF for tuberculous pericarditis: a systematic review and meta-analysis

“…However, one study had different reference diagnoses, two studies were not in English, ten studies did not contain primary data in their published article, and eight studies had inadequate samples to calculate sensitivity and specificity; thus, they were excluded from our study. Therefore, in this meta-analysis, we included nine studies 9 – 17 . Figure 1 showed the flowchart of the research collection, while Table 1 provided a summary of the included studies.…”

“…Figure 1 showed the flowchart of the research collection, while Table 1 provided a summary of the included studies. Of the nine studies included, three were carried out in Pakistan 10 , 13 , 15 , two were conducted in South Africa 12 , 14 , and the rest were carried out in Turkey 17 , Iran 9 , China 16 , and Spain 11 . All studies used a prospective observational design.…”

“…Regarding the risk of bias in the subject preference area, six studies 9 , 10 , 12 , 14 , 16 , 17 were labeled as low risk, two studies 13 , 15 were labeled as high risk, and one study 11 was labeled as an unclear risk because it did not explain the exclusion criteria clearly. The reason for the high risk of bias in this domain was due to inappropriate exclusion criteria.…”

“…The reason for the high risk of bias in this domain was due to inappropriate exclusion criteria. In the applicability concern section, we labeled one study as a low concern 12 , three studies 10 , 13 , 14 as high concerns, and five studies 9 , 11 , 15 – 17 as unclear concerns since the setting of patients was not mentioned. Studies in primary health settings were deemed low concern, whereas studies set exclusively in a tertiary care center were deemed high concern.…”

“…In the index test area, all studies included 9 – 17 were labeled as having a low risk of bias. This was because Xpert MTB/RIF provided automatic results with a prespecified threshold test, and the user received the results on a printed sheet.…”