Migrant farmworkers are among the highest-risk populations for latent tuberculosis infection (LTBI) in the United States with numerous barriers to healthcare access and increased vulnerability to infectious diseases.
[Photo: Dr. Eyal Oren]
Dr. Eyal Oren, assistant professor and infectious disease epidemiologist at the University of Arizona Mel and Enid Zuckerman College of Public Health, and colleagues examined detection methods for LTBI among migrant farmworkers along the U.S.-Mexico border. The research is published in the journal BMC Infectious Diseases.
LTBI is usually diagnosed on the border using the tuberculin skin test (TST). QuantiFERON-TB Gold In-Tube (QFT-GIT) also measures immune response against specific Mycobacterium tuberculosis antigens. The objective of the study was to assess the comparability of TST and QFT-GIT to detect LTBI among migrant farmworkers on the border, in addition to examining the effects of various demographic and clinical factors on test positivity.
Participants were recruited using mobile clinics on the San Luis US-Mexico border and tested with QFT-GIT and TST. Demographic profiles and clinical histories were collected. Kappa coefficients assessed agreement between TST and QFT-GIT using various assay cutoffs. Logistic regression examined factors associated with positive TST or QFT-GIT results.
Of 109 participants, 59 of 108 (55 percent) were either TST (34 percent) or QFT-GIT (50 percent) positive. Concordance between TST and QFT-GIT was fair (71 percent agreement). Factors associated with LTBI positivity included smoking and diabetes/high blood sugar.
The researchers found test concordance between the two tests was fair, with numerous discordant results observed. Greater proportion of positives detected using QFT-GIT may help avoid LTBI under-diagnosis. Assessment of LTBI status on the border provides evidence whether QFT-GIT should replace the TST in routine practice, as well as identifies risk factors for LTBI among migrant populations.