title: A Tuberculin Skin Test Survey and the Annual Risk of Mycobacterium tuberculosis Infection in Gambian School Children.
abstract: BACKGROUND
  A Tuberculin skin test (TST) survey was conducted to assess the prevalence of latent TB Infection (LTBI) and to estimate the annual risk of M. tuberculosis infection (ARTI) in Gambian school children. The results are expected to contribute to understanding of Tuberculosis epidemiology in The Gambia.
  
  
  METHODS
  This was a nationwide, multi-cluster survey in children aged 6-11 years. Districts, 20 of 37, were selected by probability proportional to size and schools by simple random sampling. All TST were performed using the Mantoux method. Height and weight measurements were obtained for all participants. We calculated prevalence of LTBI using cut-off points of 10mm, the mirror and mixture modelling methods.
  
  
  RESULTS
  TST readings were completed 13,386 children with median age of 9 years (interquartile range [IQR] 8-10 years). Mixture analysis yielded a cut-off point of 12 mm, and LTBI prevalence of 6.9% [95%CI 6.47-7.37] and the ARTI was 0.75% [95%CI 0.60-0.91]. LTBI was associated gender and urban residence (p <0.01). Nutritional status was not associated with non-reactive TST or sizes of TST indurations. ARTI did not differ significantly by age, gender, BCG vaccination or residence.
  
  
  CONCLUSIONS
  This estimates for LTBI prevalence and ARTI were low but this survey provides updated data. Malnutrition did not affect estimates of LTBI and ARTI. Given the low ARTI in this survey and the overlapping distribution of indurations with mixture modelling, further surveys may require complementary tests such as interferon gamma release assays or novel diagnostic tools.
authors.affiliation: Disease Control and Elimination Theme, Medical Research Council Unit-The Gambia, Atlantic Boulevard, Fajara, PO Box 273, Banjul, The Gambia.
authors.forename: Ifedayo M O
authors.initials: IM
authors.lastname: Adetifa
authors.affiliation: Disease Control and Elimination Theme, Medical Research Council Unit-The Gambia, Atlantic Boulevard, Fajara, PO Box 273, Banjul, The Gambia.
authors.forename: Abdul Khalie
authors.initials: AK
authors.lastname: Muhammad
authors.affiliation: Disease Control and Elimination Theme, Medical Research Council Unit-The Gambia, Atlantic Boulevard, Fajara, PO Box 273, Banjul, The Gambia.
authors.forename: David
authors.initials: D
authors.lastname: Jeffries
authors.affiliation: Disease Control and Elimination Theme, Medical Research Council Unit-The Gambia, Atlantic Boulevard, Fajara, PO Box 273, Banjul, The Gambia.
authors.forename: Simon
authors.initials: S
authors.lastname: Donkor
authors.affiliation: Academic Medical Centre, University of Amsterdam, Amsterdam, Netherlands.
authors.forename: Martien W
authors.initials: MW
authors.lastname: Borgdorff
authors.affiliation: Disease Control and Elimination Theme, Medical Research Council Unit-The Gambia, Atlantic Boulevard, Fajara, PO Box 273, Banjul, The Gambia.
authors.forename: Tumani
authors.initials: T
authors.lastname: Corrah
authors.affiliation: Disease Control and Elimination Theme, Medical Research Council Unit-The Gambia, Atlantic Boulevard, Fajara, PO Box 273, Banjul, The Gambia.
authors.forename: Umberto
authors.initials: U
authors.lastname: D'Alessandro
mesh_terms: D000886:Anthropometry; D001500:BCG Vaccine; D002648:Child; D016000:Cluster Analysis; D003430:Cross-Sectional Studies; D005260:Female; D005714:Gambia; D006801:Humans; D059425:Interferon-gamma Release Tests; D055985:Latent Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology / Q000276:immunology; D008297:Male; D008962:Models, Theoretical; D009169:Mycobacterium tuberculosis / Q000378:metabolism*; D009752:Nutritional Status; D015995:Prevalence; D011336:Probability; D012111:Residence Characteristics; D012307:Risk Factors; D012424:Rural Population; D012574:Schools; D014374:Tuberculin Test / Q000379:methods*; D014376:Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology / Q000276:immunology; D014505:Urban Population
chemical_list: D001500:BCG Vaccine