Microbiological outcome of trace results on Xpert MTB/RIF Ultra: An early experience at Singapore’s Tuberculosis Control Unit

The World Health Organisation recommends repeat testing of a trace result on sputum Xpert MTB/RIF Ultra(Xpert Ultra) in asymptomatic persons. Treatment should be started if repeat test shows trace results;treatment may be held if repeat is negative. The Tuberculosis Control Unit in Singapore manages 80% of the national caseload: asymptomatic persons from high TB and multi-drug resistant TB burden countries with abnormal chest x-rays account for about 40%. Most undergo 2 sets of sputum for acid-fast bacilli(AFB) smear, culture and Xpert Ultra. We report the microbiological outcomes of persons with at least 1 Xpert Ultra trace result undergoing TB evaluation from 4th May 2023 to 30th November 2023. All Xpert Ultra at initial evaluation of 76 patients were recorded. Fifty-two patients had at least 1 sample with trace result. They were divided into 3 groups according to load of other Xpert Ultra samples(Figure 1):2 trace, 1 trace and another negative, and 1 trace sample only. Forty-two (80.8%) patients had 1 trace and another negative sample, and 6(11.5%) patients had only 1 trace sample done: AFB culture was positive for MTC in 12(25%) patients,8 of whom were asymptomatic. A significant proportion of patients with a single Xpert Ultra trace result were positive for MTC on culture, two-thirds of whom were asymptomatic. Therefore, a single Xpert Ultra trace result should not be ignored in our setting. <fig><object-id>erj;64/suppl_68/PA634/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig>