ADA and tuberculosis: The low PPV of CSF-ADA in this study is a salient finding considering PPV depends on the prevalence of a given disease in the study population: TB is endemic to the Republic of Korea (70/100,000 of the population), which has a 23-fold higher incidence of TB as compared to the United States (3.1/100,000 population) (Heeae et al., 2019).