Epidemiology of extrapulmonary tuberculosis in Brunei Darussalam: a retrospective cohort study

OBJECTIVES: We reported the incidence and associated factors of extrapulmonary tuberculosis (EPTB). DESIGN: A retrospective cohort study. SETTING: Brunei Darussalam, an intermediate tuberculosis (TB)-burden country with stagnating annual TB rates. PARTICIPANTS: All active TB cases identified in the country between January 2001 and December 2018 (18 years). PRIMARY AND SECONDARY OUTCOME MEASURES: Annual proportions of EPTB (overall and specific) were calculated. Multiple logistic regression was done to investigate factors associated with developing EPTB, when compared with pulmonary TB (PTB). Χ(2) trend test was used to determine any trends during the 18-year study period. RESULTS: We identified 3916 TB cases, among which 743 (19.0%) were EPTB cases. Lymphatic (44.8%) and pleural (19.4%) EPTB were most common. The main modes of diagnosis were tissue biopsy (73.6%) and radiological assessment (18.3%). Treatment success and mortality rate were 79.7% and 7.0%, respectively. Associations with specific EPTB types varies with age-group and gender. Younger age-group (adjusted OR (aOR)≥1.94) and women (aOR: 2.45 (95% CI: 1.94 to 3.11)) had higher adjusted odds of developing lymphatic EPTB, but had lower adjusted odds of developing pleural EPTB (younger age-group (aOR≤0.54) and women (aOR: 0.41 (95% CI: 0.17 to 0.90)). When compared to foreign residents, locals had higher adjusted odds of skeletal (aOR: 4.44 (95% CI: 2.04 to 11.69)), gastrointestinal (aOR: 3.91 (95% CI: 1.84 to 9.66)) and other types of EPTB (aOR: 3.42 (95% CI: 1.53 to 9.14)). No significant trend differences were observed for overall and specific EPTB types. CONCLUSION: Despite being generally non-infectious and less recognised than PTB, understanding EPTB epidemiology is important as it also contributes to the overall TB burden in a country. Examining EPTB cases by their specific anatomical site would provide more information on risk factors. Raising public awareness on the EPTB symptoms and that TB affects lungs and other parts of the body could promote early health seeking behaviour and early EPTB diagnosis.