Diagnostic accuracy of the BD MAX MDR-TB assay on sputum and tongue swabs for Mycobacterium tuberculosis complex detection in adults under investigation for TB in South Africa

Sep 29, 2026

Despite the availability of molecular diagnostics, only 48% of newly diagnosed tuberculosis (TB) cases were confirmed with nucleic acid amplification tests in 2023. This study evaluated the BD MAX MDR-TB assay for Mycobacterium tuberculosis complex detection and rifampicin/isoniazid resistance profiling using sputum and tongue swabs from South African adults. Among 335 participants, raw sputum achieved high sensitivity and specificity versus culture, and strong agreement with Xpert MTB/RIF Ultra, while tongue swabs showed improved accuracy with a diluted STR buffer. Findings suggest tongue swabs may be feasible but require larger studies, and high MTB low POS rates emphasize careful program assessment before implementation.

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| Clinical Microbiology | Research Article Diagnostic accuracy of the BD MAX MDR-TB assay on sputum and tongue swabs for Mycobacterium tuberculosis complex detection in adults under investigation for TB in South Africa Anura David,1 Lyndel Singh,1 Manuel Pedro da Silva,2 Keneilwe Peloakgosi-Shikwambani,1 Zanele Nsingwane,1 Violet Molepo,1 Wendy Stevens,1,2 Lesley Erica Scott1 AUTHOR AFFILIATIONS See affiliation list on p. 11. ABSTRACT Despite the availability of molecular diagnostics, only 48% of newly diagnosed tuberculosis (TB) cases were confirmed using nucleic acid amplification tests in 2023. The MAX Multi Drug Resistant Tuberculosis (MAX MDR-TB) assay detects Mycobacterium tuberculosis complex (MTBC) and resistance to rifampicin (RIF) and isoniazid (INH), but data on clinical performance are limited. This study assessed the assay’s performance on sputum and tongue swabs (TSs) . The assay was evaluated for MTBC detection and RIF and INH resistance profiling on sputum using liquid culture asthe reference and Xpert MTB/RIF Ultra (Ultra) as a comparator. Diagnostic accuracy for MTBC detection on TS was also assessed. Among 335 participants (56% HIV prevalence), MAX MDR-TB on raw sputum showed an overall sensitivity and specificity of 88.7%(95% confidence interval [CI]: 78.1–95.3) and 98.2%(95% CI: 95.8–99.4) compared with culture and strong agreement with Ultra (Cohen’s kappa = 0.853) . A total of 15/55 (27%) sputum samples were classified as “MTB low POS.” Two false RIF-resistant results were observed. INH resistance was missed in two cases. Although specimen numbers were small, TS demonstrated better diagnostic accuracy when using a diluted sample treatment reagent (STR) (66%) buffer. Although the MAX MDR-TB assay demonstrated good agreement with Ultra, Ultra identified more TB cases. Preliminary findings suggest that TS, particularly with a diluted STR buffer, may be a feasible specimen type, but larger studies are required. The high frequency of MTB low POS results highlights the importance of technology assessment by TB programs prior to implementation to minimize repeat testing and enhance diagnostic reliability. IMPORTANCE This study evaluates the accuracy of the BD MAXTM MDR-TB assay in detecting Mycobacterium tuberculosis complex using sputum and tongue swabs from individuals being assessed for tuberculosis (TB) in South Africa. Rapid and reliable TB diagnosis is crucial for early treatment and preventing transmission. The MAX Multi Drug Resistant Tuberculosis (MAX MDR-TB) assay is a fully automated molecular test that can simultaneously detect TB and drug resistance, offering a potentially faster and more efficient alternative for TB diagnosis. By assessing its performance on different specimen types, this study provides valuable insights into its reliability in clinical settings. Although the MAX MDR-TB assay demonstrated strong agreement with the Xpert MTB/RIF Ultra assay, it identified fewer TB cases. Tongue swabs were also shown to be a feasible specimen type for testing. This research contributes to global TB control efforts by evaluating advanced diagnostics that could streamline testing, reduce delays, and ultimately improve patient outcomes. KEYWORDS Mycobacterium tuberculosis, BD MAX DR-TB, rifampicin, isoniazid, NAAT Editor Ana Cabrera, London Health Sciences Centre, London, Ontario, Canada Address correspondence to Anura David, [anura.david@witsdih.ac.za](anura.david@witsdih.ac.za). Professor Lesley Erica Scott reports that she owns shares and receives royalties from Smartspot Quality (Pty) Ltd, via the University of the Witwatersrand; Becton, Dickinson and Company provided an honorarium for Anura David to present at a BD Symposium during the ASLM Conference 2023. This support did not influence the content, analysis, or conclusions of this paper. All other authors declare conflicts of interest related this work I n 2023, tuberculosis (TB) reclaimed its position as the leading infect

FAQs

What does the BD MAX MDR-TB assay detect in this study?

It detects Mycobacterium tuberculosis complex (MTBC) and profiles resistance to rifampicin (RIF) and isoniazid (INH).

How was diagnostic performance assessed for sputum and tongue swabs?

MTBC detection on tongue swabs was evaluated, while sputum performance included RIF and INH resistance profiling using liquid culture as the reference and Xpert MTB/RIF Ultra as the comparator.

What did the study find about tongue swabs compared with sputum?

Tongue swabs showed better diagnostic accuracy when using a diluted sample treatment reagent (STR) buffer, and the work suggests tongue swabs may be feasible, though larger studies are needed.

Sep 29, 2026

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