Detection of latent tuberculosis infection among migrant farmworkers along the US-Mexico border.
BACKGROUND
Migrant farmworkers are among the highest-risk populations for latent TB infection (LTBI) in the United States with numerous barriers to healthcare access and increased vulnerability to 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 this study is to assess the comparability of TST and QFT-GIT to detect LTBI among migrant farmworkers on the border, as well as to examine the effects of various demographic and clinical factors on test positivity.


METHODS
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.


RESULTS
Of 109 participants, 59 of 108 (55 %) were either TST (24/71, 34 %) or QFT-GIT (52/106, 50 %) positive. Concordance between TST and QFT-GIT was fair (71 % agreement, ĸ = 0.38, 95 % CI: 0.15, 0.61). Factors associated with LTBI positivity included smoking (OR = 1.26, 95 % CI-1.01-1.58) and diabetes/high blood sugar (OR = 0.70, 95 % CI = 0.51-0.98).


CONCLUSIONS
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.
Department of Epidemiology & Biostatistics, Mel and Enid Zuckerman College of Public Health, University of Arizona, 1295 N. Martin Ave., P.O. Box 245211, Tucson, AZ, 85724, USA. eoren@email.arizona.edu.
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http://orcid.org/0000-0001-7817-3516
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Oren
Department of Epidemiology & Biostatistics, Mel and Enid Zuckerman College of Public Health, University of Arizona, 1295 N. Martin Ave., P.O. Box 245211, Tucson, AZ, 85724, USA.
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Fiero
Department of Epidemiology & Biostatistics, Mel and Enid Zuckerman College of Public Health, University of Arizona, 1295 N. Martin Ave., P.O. Box 245211, Tucson, AZ, 85724, USA.
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E
Barrett
Department of Epidemiology & Biostatistics, Mel and Enid Zuckerman College of Public Health, University of Arizona, 1295 N. Martin Ave., P.O. Box 245211, Tucson, AZ, 85724, USA.
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B
Anderson
Yuma County Health Services District, 2200 W 28th St, Yuma, AZ, 85364, USA.
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Nuῆez
Mexican Social Security Institute, Juárez, México City, Mexico.|University of Monterrey, Avenida Ignacio Morones Prieto 4500 Pte., Jesús M. Garza, 66238, San Pedro Garza García, NL, Mexico.
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F
Gonzalez-Salazar
D000293:Adolescent; D000328:Adult; D000368:Aged; D003920:Diabetes Mellitus / Q000453:epidemiology; D000067565:Farmers / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D006943:Hyperglycemia / Q000453:epidemiology; D059425:Interferon-gamma Release Tests / Q000379:methods; D055985:Latent Tuberculosis / Q000175:diagnosis / Q000453:epidemiology*; D016015:Logistic Models; D008297:Male; D008800:Mexico / Q000208:ethnology; D008875:Middle Aged; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology; D014171:Transients and Migrants / Q000706:statistics & numerical data*; D014374:Tuberculin Test / Q000379:methods; D014481:United States / Q000453:epidemiology; D055815:Young Adult
Interferon-gamma release assay; Latent tuberculosis infection; Migrants; Tuberculin skin test