title: High incidence of latent tuberculous infection among South African health workers: an urgent call for action.
abstract: METHODS
  In South Africa, health care workers (HCWs) are at two-fold greater risk of acquiring tuberculosis (TB) disease than the general population. Few studies have evaluated the risk of incident tuberculous infection.
  
  
  OBJECTIVE
  To determine the incidence and risk factors for latent tuberculous infection (LTBI) among HCWs and to compare the results of the interferon-gamma release assay (IGRA) with those of the tuberculin skin test (TST).
  
  
  METHODS
  HCWs, including medical students, underwent a TST and human immunodeficiency virus (HIV) and IGRA testing at baseline and 12 months, and IGRA at 6 months. The participants kept 12-month TB exposure logs.
  
  
  RESULTS
  Among 199 participants (150 [76%] females, median age 31 years [range 20-61]), incident LTBI was documented using IGRA in 25/97 (26%; incident rate 29 cases/100 person-years [py], 95%CI 20-44) and using TST in 25/93 (27%; incident rate 29 cases/100 py, 95%CI 19-42). Agreement between TST and IGRA was poor (44.8%, κ = 0.23). Higher annual exposure to TB cases was reported among persons with LTBI than in those who were persistently IGRA-negative (81 cases, 95%CI 61-102 vs. 50 cases, 95%CI 43-57, P < 0.01).
  
  
  CONCLUSIONS
  The high LTBI incidence and the association of incident LTBI with annual TB caseload among HCWs indicate that more effective TB infection control should be implemented in South African health care facilities.
authors.affiliation: Wits Reproductive Health and HIV Research Unit, University of the Witwatersrand, Johannesburg, South Africa; The Aurum Institute, Parktown, Johannesburg, South Africa; School of Public Health, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: K M
authors.initials: KM
authors.lastname: McCarthy
authors.affiliation: Department of Molecular Diagnostics, National Health Laboratory Service and University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: L E
authors.initials: LE
authors.lastname: Scott
authors.affiliation: Department of Molecular Diagnostics, National Health Laboratory Service and University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: N
authors.initials: N
authors.lastname: Gous
authors.affiliation: Wits Reproductive Health and HIV Research Unit, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: M
authors.initials: M
authors.lastname: Tellie
authors.affiliation: Wits Reproductive Health and HIV Research Unit, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: W D F
authors.initials: WD
authors.lastname: Venter
authors.affiliation: Department of Molecular Diagnostics, National Health Laboratory Service and University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: W S
authors.initials: WS
authors.lastname: Stevens
authors.affiliation: Infectious Diseases, Department of Epidemiology, University of North Carolina, Chapel Hill, North Carolina, USA.
authors.forename: A
authors.initials: A
authors.lastname: Van Rie
mesh_terms: D000328:Adult; D005260:Female; D006282:Health Personnel; D006801:Humans; D015994:Incidence; D017053:Infection Control / Q000379:methods; D017758:Infectious Disease Transmission, Patient-to-Professional / Q000517:prevention & control; D059425:Interferon-gamma Release Tests; D055985:Latent Tuberculosis / Q000175:diagnosis / Q000453:epidemiology* / Q000382:microbiology / Q000517:prevention & control / Q000635:transmission; D008297:Male; D008875:Middle Aged; D016273:Occupational Exposure / Q000009:adverse effects* / Q000517:prevention & control; D016272:Occupational Health; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012307:Risk Factors; D013019:South Africa / Q000453:epidemiology; D013337:Students, Medical; D013997:Time Factors; D014374:Tuberculin Test; D016526:Workload; D055815:Young Adult