A recent study published in Emerging Infectious Diseases evaluated latent tuberculosis (TB) infections (LTBIs) in the United States (US) during 2019-20.
The US Centers for Disease Control and Prevention receives the clinical and demographic data for TB cases annually from the District of Columbia and all states. LTBI is the precursor to TB and is not reported across most states. The National Health and Nutrition Examination Survey (NHANES) cycles are the primary national data source of LTBI. NHANES includes cross-sectional surveys examining the health of the non-institutionalized, civilian US population.
The study and findings
In the present study, researchers evaluated LTBIs in the US during the 2019-20 NHANES cycle. Data collection during this cycle was halted in March 2020 due to the coronavirus disease 2019 (COVID-19) pandemic. As a result, only 18 (out of 30) sampling units were completed, and the sample was non-representative nationally. Therefore, the team used a partial unweighted dataset for analysis.
The survey examined LTBI among older people aged 60 or above and non-US-born individuals aged > 6. Participants were tested for TB using an interferon-γ release assay. These specific sub-populations were selected due to the potential of TB complications in older subjects, the high risk of LTBI-to-TB progression in non-US-born individuals, and the high test positivity in these individuals in prior studies.
A single laboratory provided all test results. In 2019-20, 837 individuals born outside the US jurisdictions were evaluated. Of these, 85 individuals (10%) were positive for TB, including 43 (51%) non-Hispanic Asian individuals and 30 (35%) Hispanic persons. Most test-positive individuals (79%) had lived in the US for at least five years.
Overall, 1,123 older subjects, including non-US- and US-born individuals, were tested for TB. Of these, 81 individuals (7%) were TB-positive, including 35 (43%) non-Hispanic black individuals. In the older age group, test-positive individuals were less likely to be non-Hispanic White, have a high-school diploma, and are more likely to be non-US born and live in poverty.
In summary, while non-representative of the US population, results from the 2019-20 NHANES cycle show that TB remained a significant health concern among older individuals and people not born in the US. Therefore, these sub-populations should be prioritized for testing and treatment with appropriate regimens to prevent the active progression of TB.
TB-positive individuals in both sub-populations were more likely to be from ethnic and racial minority groups, living in poverty, and not have a high school diploma compared to all participants in these sub-populations. Moreover, older test-positive subjects were more likely to be non-US-born than all older participants.
Comparisons between the current and previous NHANES cycles were limited due to changes in the classification of participants by birth country. For instance, in 2019-20, subjects were considered to be born in the US if their birth occurred in a US state, the District of Columbia, and US-affiliated territories. Contrastingly, in 2011-12, people born in US-affiliated territories were deemed non-US-born. Thus, consistency in the definition of the birth country would be essential for future cycles.