Abstract:

Objective To evaluate the performance of GeneXpert MTB/RIF Ultra (Xpert Ultra) for pulmonary tuberculosis (PTB) diagnosis in children using gastric juice. Methods In this retrospective study, a total of 173 eligible children were enrolled, who admitted to Pediatric Department of the 1st People’s Hospital of Liangshan Yizu Autonomous Prefecture between July 2019 and July 2020. Using composite reference standard (CRS) as reference, 114 of them were diagnosed with PTB (case group), and 59 were non-TB patients with other respiratory infectious diseases (control group). Gastric juice and sputum samples were collected and subjected to culture and Xpert Ultra. The performance of Xpert Ultra was evaluated in gastric juice and sputum samples using CRS as gold standard. Results Using CRS as reference, the diagnostic sensitivity, specificity, accordance rate and Kappa value of Xpert Ultra for PTB diagnosis in children using gastric juice samples was 53.5% (61/114), 98.3% (58/59), 68.8% (119/173) and 0.43, respectively. The sensitivity of Xpert Ultra using gastric juice samples in pre-school (0-6 years) children was significantly higher than that in school-aged (6-14 years) children (66.7% (26/39) vs. 46.7% (35/75),χ²=4.126, P=0.042). The sensitivity of MTB culture was only 20.2% (23/114). Among 65 children who underwent Xpert Ultra of both gastric juice and sputum samples, the sensitivity of Xpert Ultra in gastric juice samples was higher than that in sputum samples (52.2% (24/46) vs. 43.5% (20/46)). However, the difference was not significant (χ²=0.697, P=0.404). Among 150 culture-negative children, 40 were positive using Xpert Ultra, in which trace result accounted for 37.5% (15/40). The percentage of trace result was only 14.3% (3/21) among culture-positive children. Five children were found to be rifampicin resistant among 61 Xpert Ultra-positive patients. Conclusion The performance of Xpert Ultra for PTB diagnosis in children using gastric juice samples is good, making it useful for early diagnosis of pediatric TB. The gastric juice samples are valuable alternative types for those who can’t expectorate or preschool children who can’t provide qualified sputum samples.

Key words: Child, Tuberculosis, Gastric juice, Early diagnosis, Molecular diagnostic techniques