Abstract:

Objective To evaluate the value of GeneXpert MTB/RIF (GeneXpert) in tuberculosis (TB) diagnosis by testing gastric juice obtained from children who are suspected to be pulmonary TB.Methods A total of 155 TB suspects aged from 2 months to 14 years, who were admitted to the Department of Pediatric TB of Harbin Chest Hospital, the Department of Respiration of Harbin Children’s Hospital and the Department of Pediatrics of the First Affiliated Hospital of Harbin Medical University from September 2017 to December 2018, were enrolled into this study. Among them, 115 children were clinically diagnosed as pulmonary TB while 40 children were diagnosed as non-TB. All enrolled patients were taken fasting gastric juice in the morning and the samples were performed the following examinations: fluoresce smear microscopy (smear examination), BACTEC MGIT 960 liquid culture (MGIT 960 method) and GeneXpert. The clinical diagnosis results were regarded as the standard, the diagnostic efficacy of smear, MGIT 960 and GeneXpert in gastric juice was evaluated; and then the MGIT 960 susceptibility test results were regarded as the standard, the efficacy of GeneXpert in detecting rifampicin resistant MTB was evaluated.Results When the clinical diagnosis results were regarded as the standard, the sensitivity of smear examination, MGIT 960 method and GeneXpert in detection of pediatric pulmonary TB was 30.4% (35/115), 54.8% (63/115), 69.6% (80/115) and the specificity was 95.0% (38/40), 100.0% (40/40), 97.5% (39/40), respectively. In 115 cases who were clinically diagnosed as pulmonary TB, the positive rates of GeneXpert test were 96.7% (29/30), 81.8% (27/33) and 40.4% (19/47) respectively among the TB children with smear positive and culture positive, smear negative and culture positive, smear negative and culture negative; the number of patients with positive GeneXpert test result was 5 (5/5) in children with smear positive and culture negative; the positive rate of GeneXpert test was 97.1% (34/47), 57.5% (46/80) and 46.2% (24/52) in the children with smear positive, smear negative and culture negative. When the MGIT 960 culture results were regarded as the standard, the sensitive of GeneXpert was 88.9% (56/63). Among 115 children who were clinically diagnosed as pulmonary TB, 56 cases were positive for both MGIT 960 culture and GeneXpert test; 11 cases were rifampicin resistance with MGIT 960 test while 45 cases were rifampicin sensitive; 13 cases were rifampicin resistance with GeneXpert test while 43 cases were rifampicin sensitive. When the MGIT 960 drug susceptibility test was regarded as the standard, the sensitivity of GeneXpert test was 100.0% (11/11) in diagnosis of rifampicin resistant MTB and its specificity was 95.6% (43/45), which was in good consistency with MGIT 960 susceptibility test (Kappa value=0.894). Conclusion >GeneXpert test has high sensitivity and specificity in MTB detection in gastric juice of children with TB, and has a high detection rate too in pediatric TB patients with culture negative. The detection of rifampicin resistant MTB by using GeneXpert test was also in high consistency with using MGIT 960 drug sensitivity test, which has a good application value in the diagnosis of pediatric TB and proving guidance of treatment.

Key words: Child, Tuberculosis, pulmonary, Gastric juice, Nucleic acid amplification techniques, Nucleic acid probes, Diagnostic techniques and procedures, Comparative study