ARTICLE: Evidence for tuberculosis in individuals with Xpert Ultra "trace" sputum during screening of high-burden communities
AUTHORS: Joowhan Sung, Mariam Nantale, Annet Nalutaaya, Patrick Biché, James Mukiibi, Caleb E Kamoga, Joab Akampurira, Francis Kayondo, Rogers Kiyonga, Michael Mukiibi, Olga Nakasolya, Molly McGeehan, David W Dowdy, Achilles Katamba, Emily A Kendall
JOURNAL: Clin Infect Dis. 2023 Oct 3:ciad595. doi: 10.1093/cid/ciad595. Online ahead of print.
Background: "Trace" results on Xpert MTB/RIF Ultra ("Ultra") - a molecular diagnostic test for tuberculosis (TB) - are often interpreted as an indication for TB treatment, but may also represent detection of nonviable bacilli or analytical error. In community screening settings where individual TB risk is low, there is limited guidance on how to interpret Ultra-trace results.
Methods: We conducted systematic Ultra TB screening of adults and adolescents (≥15 years) in Kampala, Uganda through door-to-door and event-based sputum collection. We enrolled individuals with trace-positive sputum for detailed clinical, radiographic, and microbiological (including two sputum cultures, repeat Ultra, and for people with HIV, urine lipoarabinomannan) evaluation, and compared those findings to similar evaluations in controls with Ultra-negative and Ultra-positive (non-trace) sputum.
Results: Of 21,957 people screened with Ultra, 211 (1.0%) tested positive, including 96 (46% of positives) with trace results. Of 92 people enrolled with trace-positive sputum; 12% (11/92) were HIV-positive and 14% (13/92) had prior TB. The prevalence of TB among participants with trace-positive sputum results was 14% (13/92) by culture, 24% (22/92) using broader microbiological criteria, and 26% (24/92) after accounting for clinical diagnosis. The prevalence of cough and of abnormal chest CT findings were 32% and 26%, respectively, if Ultra-negative; 34% and 54% if trace-positive/non-microbiologically confirmed; 71% and 95% if trace-positive/microbiologically confirmed; and 72% and 92% if Ultra-positive (more than trace).
Conclusion: Most individuals with trace-positive sputum in Ugandan communities did not have microbiologically confirmed TB but had more symptoms and chest CT abnormalities than people with Ultra-negative sputum.
Keywords: Xpert MTB/RIF Ultra; Xpert Ultra; community screening; trace; tuberculosis.
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