Accuracy of Nasopharyngeal Aspirate GeneXpert Compared to Gastric Aspirate TB Culture and GeneXpert in Diagnosing Pulmonary Tuberculosis in Pediatric Patients

Background: Pulmonary TB in children remains to be a burden in the Philippines. Diagnosis remains to be a challenge for pediatricians due to its paucibacillary nature, difficulty in obtaining specimens, cost of test as well as the varied sensitivity of the different tests available. Gastric aspirate (GA), commonly used for bacteriological diagnosis of pulmonary tuberculosis (PTB) in children, involves an invasive procedure that may cause discomfort and sometimes require admission. Nasopharyngeal aspirate (NPA), on the other hand, can be easily and non-invasively obtained but is currently not a recommended specimen for testing for PTB. Objectives: This study aims to determine the accuracy of NPA GeneXpert in diagnosing PTB among pediatric patients 0-18 years old with presumptive TB using GA GeneXpert as the initial screening test and GA TB culture as gold standard. Methodology: This prospective, cross-sectional diagnostic study involved collection of single NPA and GA specimens for GeneXpert and TB culture in 100 patients with presumptive PTB seen at a tertiary government hospital in the Philippines. Results: Of the one hundred pediatric patients (mean age 6 ± 5.63 years) enrolled, 50 were clinically diagnosed PTB, 16 bacteriologically-confirmed and 34 were not PTB disease. Sensitivity, specificity and predictive values with 95% confidence intervals of the NPA GeneXpert were determined compared to GA GeneXpert and GA culture. Sensitivity, specificity, positive and negative predictive values of the NPA GeneXpert compared to GA GeneXpert were 70%, 96.67%, 70% and 96.67%, respectively. While NPA GeneXpert compared to GA TB culture were 40%,91.58%, 20% and 96.67%, respectively. Conclusion: GeneXpert testing on a single NPA specimen is a highly specific and rapid test that can be used to diagnose PTB in pediatric patients, particularly where gastric aspiration or mycobacterial culture is not feasible.