EXPERIENCE WITH USING RAPID MOLECULAR TESTING IN DIAGNOSING PULMONARY AND EXTRA-PULMONARY PEDIATRIC TUBERCULOSIS IN A NON-ENDEMIC SETTING - A RETROSPECTIVE CASE SERIES

Abstract

BACKGROUND: Tuberculosis (TB) is a rare but potentially devastating infection among Canadian children. Accurate diagnosis and initiation of treatment are limited in part by the fact that it takes 2-6 weeks for culture results to be confirmed. Xpert MTB/RIF (Xpert) is a rapid, automated molecular assay that has been validated for diagnosing pulmonary but not extra-pulmonary TB in children. OBJECTIVE(S): This was a retrospective study of children investigated for active TB at our facility in order to: 1.Outline demographic characteristics and describe clinical presentations of children diagnosed with active TB. 2.Compare performance of molecular testing (Xpert) to stain and Mycobacterium tuberculosis culture on pulmonary and extra-pulmonary specimens. DESIGN/METHODS: We conducted a retrospective chart review of all paediatric patients investigated for active TB at our facility with stain, culture and molecular (Xpert) testing between January 2015 and August 2017. Due to a small number of patients, our data analysis was limited to narrative summary and descriptive statistics. RESULT(S): A total of 10 children were diagnosed with active TB, including 3 cases of pulmonary, 4 extra-pulmonary and 3 disseminated disease. Age range at diagnosis was 2 months to 16 years, with 3 children younger than 1 year. Most children contracted TB while travelling to and/or being exposed to an index case from endemic areas, including East Asia/Western Pacific (5), South Asia (2) and Africa (1). All children were HIV negative. Time from symptom onset to TB diagnosis and treatment ranged from approximately 4 days to 5 months. Multi-drug resistant TB was confirmed in 1 child. Sadly, 1 child passed away from TB related complications. AFB stain was positive on at least one specimen in 4/10 cases, cultures were positive in 8/10 and molecular testing (Xpert) in 7/10 cases. Time to positive cultures ranged from 10 to 35 days, with an average of 19 days. All cases positive on Xpert were also culture positive. Xpert test diagnosed TB in 5/6 of extra-pulmonary specimens submitted, including pericardial fluid, lymph node tissues and cerebrospinal fluid. CONCLUSION(S): Many paediatric TB patients at our facility are children who have traveled to/have contacts from TB endemic regions, emphasizing the need for obtaining thorough exposure and travel history. Culture and molecular testing demonstrated similar TB detection rates, albeit based on a small patient population. While cultures remain the most reliable diagnostic method, molecular testing may facilitate rapid diagnosis and treatment of pulmonary and extra-pulmonary paediatric TB in a non-endemic setting.