Xpert MTB/RIF Ultra is highly sensitive for the diagnosis of tuberculosis lymphadenitis in an HIV-endemic setting

Background Tuberculosis lymphadenitis (TBL) is the most common extrapulmonary TB (EPTB) manifestation. Xpert MTB/RIF Ultra (Ultra) is a World Health Organization-endorsed diagnostic test, but performance data for TBL, including on non-invasive specimens, are limited. Methods Fine needle aspiration biopsies (FNABs) from outpatients (≥18 years) with presumptive TBL (n=135) underwent: 1) routine Xpert (later Ultra once programmatically available), 2) a MGIT960 culture (if Xpert- or Ultra-negative, or rifampicin-resistant), and 3) study Ultra. Concentrated paired urine underwent Ultra. Primary analyses used a microbiological reference standard (MRS). Results In a head-to-head comparison (n=92) of FNAB study Ultra and Xpert, Ultra had increased sensitivity [91% (95% confidence interval 79, 98) vs. 72% (57, 84); p=0.016] and decreased specificity [76% (61, 87) vs. 93% (82, 99); p=0.020], and detected patients not on treatment. HIV nor alternative reference standards affected sensitivity and specificity. In patients with both routine and study Ultras, the latter detected more cases [+20% (0, 42); p=0.034] and, further indicative of potential laboratory-based room-for-improvement, false-negative study Ultras had more PCR inhibition than true-positives. Study Ultra “false-positives” had less mycobacterial DNA than “true-positives” [trace-positive proportions 59% (13/22) vs. 12% (5/51); p<0.001]. Exclusion or recategorization of “traces” removed potential benefits offered over Xpert. Urine Ultra had low sensitivity [18% (7, 35)]. Conclusions Ultra on FNABs is highly sensitive and detects more TBL than Xpert. Patients with FNAB Ultra-positive “trace” results, most of whom will be culture-negative, may require additional clinical investigation. Urine Ultra could reduce the number of patients needing invasive sampling. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement The work was funded by the South African Medical Research Council, Stellenbosch University Faculty of Health Sciences, and the National Research Foundation. Grant Theron acknowledges funding from the EDCTP2 programme supported by the European Union (grant SF1401, OPTIMAL DIAGNOSIS) and the National Institute of Allergy and Infection Diseases of the National Institutes of Health (U01AI152087). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study was approved by the Stellenbosch University Human Research Ethics Committee and Tygerberg General Hospital (TGH) (both N16/04/050) All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes Available from the corresponding author.