Abstract
Nearly one-third of the world’s population is infected with latent tuberculosis (LTBI). Tuberculosis (TB) rates in the border states are higher than national rates in both the US and Mexico, with the border accounting for 30% of total registered TB cases in both countries. However, LTBI rates in the general population in Mexican border states are unknown. In this region, LTBI is diagnosed using the tuberculin skin test (TST). New methods of detection more specific than TST have been developed, although there is currently no gold standard for LTBI detection. Our objective is to demonstrate utility of the Quantiferon TB gold In-Tube (QFT-GIT) test compared with the TST to detect LTBI among border populations. This is an observational, cross-sectional study carried out in border areas of the states of Nuevo Leon and Tamaulipas, Mexico. Participants (n = 210) provided a TST and blood sample for the QFT-GIT. Kappa coefficients assessed the agreement between TST and QFT-GIT. Participant characteristics were compared using Fisher exact tests. Thirty-eight percent of participants were diagnosed with LTBI by QFT-GIT. The proportion of LTBI detected using QFT-GIT was almost double [38% (79/210)] that found by TST [19% (39/210)] (P < 0.001). Concordance between TST and QFT-GIT was low (kappa = 0.37). We recommend further studies utilizing the QFT-GIT test to detect LTBI among border populations.
Highlights
Most US–Mexico border states have high rates of unemployment and low per capita income [1]
Patients with active TB disease were referred for follow-up but excluded from the study, family members of these active TB patients were invited to participate in the study
Participants In this preliminary work in the border states of Nuevo Leon and Tamaulipas, Mexico, we evaluated 210 participants
Summary
Most US–Mexico border states have high rates of unemployment and low per capita income [1] In these states, overcrowding, poor nutrition, and poor access to health services are common [2]. The US–Mexico border region, extending 37 miles north and south of the border itself, accounts for 30% of total registered tuberculosis (TB) cases in both the US and Mexico [2], and border states from Northern Mexico have the highest rates of TB in the country, with rates between 15 and 39 cases per 100,000 inhabitants [3,4,5,6] Those border states with the highest rates, such as in Baja California, Sonora, and Latent TB in border populations. The migratory process itself, poverty, and substandard conditions are likely to be primary factors resulting in increased risk of developing active TB [5, 6, 11]
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