Is Xpert MTB/Rif Ultra superior to Xpert MTB/Rif for the diagnosis of tuberculosis in children in Uzbekistan

<b>Abstract:</b> Early detection of tuberculosis (TB) among children are essential to prevent the further morbidity and mortality. Using the national reference laboratory database in Uzbekistan, we evaluated the performance of Xpert MTB/Rif Ultra (Xpert Ultra) vs Xpert MTB/Rif (Xpert) considering traces as positive results, and using liquid culture as a gold standard. The study was carried out for the first time in Uzbekistan. <b>Methods:</b> We used the results of 342 various specimens of all children less than 18 years old with presumptive and diagnosed TB that were consecutively tested for MTB using Xpert Ultra and Xpert between July 2017 to June 2020. <b>Results:</b> The proportions of diagnosed TB in the sample was 6.4%. The diagnostic sensitivities were 88.9% (95% CI: 51.8 – 99.7) for Xpert Ultra and 70.0% (95% CI: 34.8 – 93.3) for Xpert. Specificities of Xpert Ultra and Xpert were 93.9% (95% CI: 88.2 – 97.0) and 96.5% (95% CI: 92.0 – 98.9) respectively. When considering trace call as negative on Xpert Ultra, the sensitivity dropped to 66.7% (95% CI: 29.6% – 92.5%) while specificity remained comparable at 95.5% (95% CI: 90.4% – 98.3%). In conclusion, the results show promis; however, because of the overlappes in CIs, we did not find evidence for Xpert Ultra being superior to Xpert. Prospective studies need to evaluate the performance of Xpert Ultra ensuring a larger sample size.