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The following is a summary of “Improved detection of extrapulmonary and paucibacillary pulmonary tuberculosis by Xpert MTB Host Response in a TB low endemic, high resource setting,” published in the March 2025 issue of Journal of Infectious Diseases by Folkesson et al. 

The Xpert MTB-Host Response (MTB-HR) test has demonstrated success in detecting pulmonary tuberculosis (PTB) with high bacterial levels, meeting WHO performance standards.  

Researchers conducted a retrospective study to assess the role of MTB-HR as a non-sputum, near point-of-care (POC) method for diagnosing extrapulmonary tuberculosis (EPTB) and paucibacillary PTB.  

They assessed 307 individuals with presumed TB in Stockholm, Sweden, and performed MTB-HR venous and capillary testing in parallel. Clinical characterization was based on symptoms, microbiological tests (microscopy, PCR, and culture), radiological assessment, and routine biochemical tests. The ROC analysis was performed for PTB and EPTB to determine cut-offs optimizing sensitivity and specificity, including WHO targets for screening and diagnostic tests.  

The results showed that MTB-HR exhibited strong performance in microbiologically confirmed PTB (AUC 0.84; 95% CI: 0.78-0.90, n=69) and EPTB (AUC 0.82; 95% CI: 0.75-0.90, n=34). Using Youden index cut-offs, the NPV was high in microscopy- and PCR-negative PTB (-1.27, NPV 94%) and EPTB (-1.58, NPV 95%), meeting the minimum TPP sensitivity for confirmed EPTB. Among individuals without TB (n=204), most had pulmonary infectious diseases. Venous and capillary sample results showed a near-perfect correlation (r=0.97, P <0.001).  

Investigators concluded the Capillary Xpert MTB-HR test enhanced the detection of PCR-negative TB, showed promise for ETB, correlated with bacterial load, and would be more clinically useful as a graded score. 

Source: academic.oup.com/jid/advance-article/doi/10.1093/infdis/jiaf110/8053009