article · Scientific Reports
Extrapulmonary tuberculosis presents ongoing diagnostic difficulties. This research evaluated the diagnostic accuracy of the Xpert MTB/RIF Ultra molecular test using 847 extrapulmonary specimens gathered between 2017 and 2021 in Tunisia. Test performance was assessed against standard culture results, alongside microscopy. Overall, the molecular tool achieved a sensitivity of 80.66 percent and a specificity of 70.87 percent. Diagnostic performance varied noticeably depending on the biological sample origin. The test reached perfect sensitivity of 100 percent in cerebrospinal fluid, bone and joint, and cutaneous samples, accompanied by specificity levels between 70.60 and 91.11 percent. For lymph node aspirates and biopsies, sensitivity reached 87.50 percent, but specificity was lower at 51.08 percent. For pleural specimens, sensitivity was 77.50 percent and specificity was 79.56 percent. Combining this molecular tool with other diagnostic methods could enhance its overall utility.
Tuberculosis occurring outside the lungs is notoriously difficult to identify promptly using standard techniques. By testing hundreds of clinical specimens, this evaluation demonstrates where a rapid molecular assay performs reliably and where its limitations lie. Understanding these variations helps medical laboratories select appropriate testing strategies to detect infections faster and avoid misdiagnosis across different bodily sites.
This work assesses a commercial diagnostic product, Xpert MTB/RIF Ultra, directly within clinical laboratory workflows. It provides real-world validation data for hospital laboratories, public health programmes, and clinical diagnostic providers seeking to implement or refine testing protocols for extrapulmonary tuberculosis. The technology itself is commercially available and ready for clinical deployment, although the findings indicate it requires pairing with complementary diagnostic methods in specific sample types.
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Extrapulmonary tuberculosis (EPTB) remains a challenging diagnosis. The purpose of this study was to assess the accuracy of Xpert MTB/RIF Ultra (Cepheid, USA) for rapid diagnosis of EPTB in Tunisia. Eight hundred and forty-seven extrapulmonary samples collected from 2017 to 2021, were subjected to Xpert MTB/RIF Ultra. Microscopy and culture were performed for all the specimens. The accuracy of Xpert Ultra was evaluated in comparison to the culture. Xpert Ultra diagnosed EPTB with a global sensitivity of 80.66% (74.3-85.75) and specificity of 70.87% (67.31-74.20). The molecular test was most accurate when performed in cerebrospinal fluids, bones and joints and cutaneous specimens showing a sensitivity of 100% and a specificity ranging from 70.60 to 91.11%. In lymph node samples comprising aspirates and biopsies, the sensitivity of Xpert Ultra was high 87.50% (77.23-93.53), however, the specificity was 51.08% (44.67-57.46). For pleural samples, the Xpert Ultra sensitivity was 77.50% (68.34-84.68) ranging from 71.43 to 80% in pleural biopsies and fluids respectively. The specificity in all pleural specimens was 79.56% (74.40-83.91). Xpert Ultra showed promise in the diagnosis of EPTB. The performances varied according to the site of the disease. The test may be more valuable if used in combination with other diagnostic modalities.
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DOI: 10.1038/s41598-024-52130-3
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