Epidemiology of concurrent extrapulmonary tuberculosis in inpatients with extrapulmonary tuberculosis lesions in China: a large-scale observational multi-centre investigation

Aims: A high proportion of all tuberculosis (TB) cases present with extrapulmonary tuberculosis (EPTB), including concurrent EPTB involving more than one extrapulmonary lesion site within the body. However, previous reports only characterised lesions of single-site EPTB cases. This study aimed to investigate epidemiological characteristics and association rules of concurrent EPTB cases in China. Methods: An observational multi-centre study was carried out in China from Jan 2011 to Dec 2017 that included a total of 208,214 patients with EPTB lesions. Multivariable logistic regression analysis was used to identify associations between gender and age with concurrent EPTB. Association rules were analysed for significance using the Apriori algorithm. Results: The most prevalent form of EPTB lesion was tuberculous pleurisy (49.8%), followed by bronchial tuberculosis (14.8%) and tuberculous meningitis (7.6%). The most predominant concurrent EPTB case type was tuberculous pleurisy concurrent with tuberculous peritonitis (1.80%). Altogether 22 association rules were identified that included 20 strong association rules, among which highest confidence rates were found for tuberculous myelitis concurrent with tuberculous meningitis and sacral TB concurrent with lumbar vertebral TB. Moreover, association rules of EPTB concurrent with other EPTB types were found to vary with gender and age. The confidence rate of tuberculous myelitis concurrent with tuberculous meningitis was higher in females (83.67%) than males and highest in patients of ages 25-34 years (87.50%). Conclusions: Many types of concurrent EPTB were found. Thus, greater awareness of concurrent EPTB disease characteristics is needed to ensure timely clinical diagnosis and treatment of this disease.