Abstract
The diagnosis of extrapulmonary tuberculosis (EPTB) is often challenging due to paucibacillary nature of the disease. Xpert MTB/RIF Ultra (Ultra) has been developed to improve detection of Mycobacterium tuberculosis complex (MTC) in paucibacillary specimens. The objective of the study was to assess the performance of Ultra for the diagnosis of EPTB in a high-income low TB prevalence country. Extrapulmonary samples received for TB diagnostics at two hospitals in Norway between January 2015 and January 2016 were prospectively and consecutively included. Defrosted samples were subjected to Ultra. Culture and routine PCR tests were used as reference standard. A total of 82 samples, 10 culture and/or routine PCR positive (confirmed TB) samples and 72 culture and routine PCR negative samples were included in analysis. The overall sensitivity and specificity of Ultra were 90% (9/10, 95% CI 56–100) and 99% (71/72, 95% CI 93–100), respectively. Ultra was positive in 6/7 smear negative confirmed TB samples. To conclude, Ultra showed a high sensitivity and specificity in extrapulmonary specimens and may contribute to a rapid diagnosis of EPTB in a low TB prevalence setting.
Highlights
The diagnosis of extrapulmonary tuberculosis (EPTB) is often challenging due to paucibacillary nature of the disease
Culture and/or routine PCR test positive samples were categorised as confirmed TB samples, and culture and routine PCR test negative samples were categorised as non-TB samples
Frozen material was available from a total of 177 samples received for TB diagnostics during the study period, and comprised 21 biopsies, 16 lymph node Fine needle aspirates (FNAs), 16 pus samples and 124 fluid samples
Summary
The diagnosis of extrapulmonary tuberculosis (EPTB) is often challenging due to paucibacillary nature of the disease. Ultra showed a high sensitivity and specificity in extrapulmonary specimens and may contribute to a rapid diagnosis of EPTB in a low TB prevalence setting. The rapid and fully automated assay simultaneously detects Mycobacterium tuberculosis complex (MTC) species, the causative agents of TB, and rifampicin resistance (RIF-R), and has a high sensitivity for diagnosing pulmonary TB (PTB) in smear positive sputum s amples[4]. The aims of the present study were to (1) evaluate the diagnostic accuracy of Ultra for diagnosing EPTB compared to routinely used culture and PCR tests in a clinical setting in the high-income low TB prevalence country N orway[26], and (2) investigate the potential of Ultra as an add-on test to the existing routine tests to improve the rapid diagnosis of EPTB
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