Evaluation of the Xpert MTB Host Response assay for the triage of patients with presumed pulmonary tuberculosis: a prospective diagnostic accuracy study in Viet Nam, India, the Philippines, Uganda, and South Africa
Authors: Ankur Gupta-Wright, Huy Ha, Shima Abdulgadar, Rebecca Crowder, Jerusha Emmanuel, Job Mukwatamundu, Danaida Marcelo, Patrick P J Phillips, Devasahayam Jesudas Christopher, Nguyen Viet Nhung, Grant Theron, Charles Yu, Payam Nahid, Adithya Cattamanchi, William Worodria, Claudia M Denkinger, Balamugesh Thangakunam, Deepa Shankar, Vinita Ernest, Flavita John, Bharath Karthikeyan, Reena Sekar, Divya Mangal, Sai Vijayasree, Swetha Sankar, Mary Shibiya, Priyadarshini Gajendran, Shanmugasundaram Elango, Rajasekar Sekar, Jared Almonte, Ramon Basilio, Asella Ruvijean Cariaga, Raul Destura, Victoria Dalay, Karlo Dayawon, Darecil Gelina, Joseph Aldwin Goleña, Maria Marissa Golla, Gidalthi Jonathan Ilagan, Dodge Lim, Angelita Pabruada, Annalyn Reyes, Roeus Vincent Arjay G. Reyes, Maricef Tonquin, Brigitta Derendinger, Megan Hendrikse, Anna Okunola, Zaida Palmer, Alfred Andama, Esther Kisakye, Job Mukwatamundu, Sandra Mwebe, Martha Nakaye, William Worodria, Justine Nyawere, Alice Bukirwa, Wilson Mangeni, John Baptist Ssonko, Annet Nakaweesa, Irene Nassuna, Irene Nekesa, David Katumba, Lucy Asege, Talemwa Nalugwa, Hai Dang, Luong Dinh, Thien Doan, Hang Do, Tam Do, Hien Le, Nguyet Le, Anh Nguyen, Dong Nguyen, Hanh Nguyen, Hoang Nguyen, Thanh Nguyen, Nam Pham, Thuong Pham, Ha Phan, Trang Trinh, Robert Castro, Catherine Cook, Tessa Mochizuki, Midori Kato-Maeda, Ruvandhi Nathavitharana, Kevin Nolan, Ioana-Diana Olaru, Maria del Mar Castro Noriega, Seda Yerlikaya
Journal: The Lancet Global Health (2024)

BackgroundNon-sputum-based triage tests for tuberculosis are a priority for ending tuberculosis. We aimed to evaluate the diagnostic accuracy of the late-prototype Xpert MTB Host Response (Xpert HR) blood-based assay.MethodsWe conducted a prospective diagnostic accuracy study among outpatients with presumed tuberculosis in outpatient clinics in Viet Nam, India, the Philippines, Uganda, and South Africa. Eligible participants were aged 18 years or older and reported cough lasting at least 2 weeks. We excluded those receiving tuberculosis treatment in the preceding 12 months and those who were unwilling to consent. Xpert HR was performed on capillary or venous blood. Reference standard testing included sputum Xpert MTB/RIF Ultra and mycobacterial culture. We performed receiver operating characteristic (ROC) analysis to identify the optimal cutoff value for the Xpert HR to achieve the target sensitivity of 90% or more while maximising specificity, then calculated diagnostic accuracy using this cutoff value. This study was prospectively registered with ClinicalTrials.gov, NCT04923958.FindingsBetween July 13, 2021, and Aug 15, 2022, 2046 adults with at least 2 weeks of cough were identified, of whom 1499 adults (686 [45·8%] females and 813 [54·2%] males) had valid Xpert HR and reference standard results. 329 (21·9%) had microbiologically confirmed tuberculosis. Xpert HR had an area under the ROC curve of 0·89 (95% CI 0·86–0·91). The optimal cutoff value was less than or equal to –1·25, giving a sensitivity of 90·3% (95% CI 86·5–93·3; 297 of 329) and a specificity of 62·6% (95% CI 59·7–65·3; 732 of 1170). Sensitivity was similar across countries, by sex, and by subgroups, although specificity was lower in people living with HIV (45·1%, 95% CI 37·8–52·6) than in those not living with HIV (65·9%, 62·8–68·8; difference of 20·8%, 95% CI 13·0–28·6; p<0·0001). Xpert HR had high negative predictive value (95·8%, 95% CI 94·1–97·1), but positive predictive value was only 40·1% (95% CI 36·8–44·1). Using the Xpert HR as a triage test would have reduced confirmatory sputum testing by 57·3% (95% CI 54·2–60·4).InterpretationXpert HR did not meet WHO minimum specificity targets for a non-sputum-based triage test for pulmonary tuberculosis. Despite promise as a rule-out test that could reduce confirmatory sputum testing, further cost-effectiveness modelling and data on acceptability and usability are needed to inform policy recommendations.FundingNational Institute of Allergy and Infectious Diseases of the US National Institutes of Health.TranslationsFor the Vietnamese and Tagalog translations of the abstract see Supplementary Materials section.