title: Contact tracing investigation after professional exposure to tuberculosis in a Swiss hospital using both tuberculin skin test and IGRA.
abstract: METHODS
  A 950 bed teaching hospital in Switzerland.
  
  
  OBJECTIVE
  To describe the result of a contact investigation among health care workers (HCW) and patients after exposure to a physician with smear-positive pulmonary tuberculosis in a hospital setting using standard tuberculin skin tests (TST) and Interferon-gamma release assay (IGRA).
  
  
  METHODS
  HCW with a negative or unknown TST at hiring had a TST two weeks after the last contact with the index case (T0), repeated six weeks later if negative (T6). All exposed HCW had a T-SPOT.TB at T0 and T6. Exposed patients had a TST six weeks after the last contact, and a T-SPOT.TB if the TST was positive.
  
  
  RESULTS
  Among 101 HCW, 17/73 (22%) had a positive TST at T0. TST was repeated in 50 at T6 and converted from negative to positive in eight (16%). Twelve HCW had a positive T-SPOT.TB at T0 and ten converted from negative to positive at T6. Seven HCW with a positive T-SPOT.TB reverted to negative at T6 or at later controls, most of them with test values close to the cut-off. Among 27 exposed patients tested at six weeks, ten had a positive TST, five of them confirmed by a positive T-SPOT.TB.
  
  
  CONCLUSIONS
  HCW tested twice after exposure to a case of smear-positive pulmonary TB demonstrated a possible conversion in 10% with T-SPOT and 16% with TST. Some T-SPOT.TB reverted from positive to negative during the follow-up, mostly tests with a value close to the cut-off. Due to the variability of the test results, it seems advisable to repeat the test with values close to the cut-off before diagnosing the presence of a tuberculous infection.
authors.affiliation: Service de Médecine Préventive Hospitalière , CHUV, Lausanne, Switzerland; Servizio di prevenzione delle infezioni e medicina del personale, Ente Ospedaliero Cantonale, Ticino, Switzerland; Swiss Medical Society for Occupational Health in Health Care F.
authors.forename: Carlo
authors.initials: C
authors.lastname: Balmelli
authors.affiliation: Service de Médecine Préventive Hospitalière , CHUV, Lausanne, Switzerland; Swiss Medical Society for Occupational Health in Health Care Facilities, Switzerland.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Zysset
authors.affiliation: Reparto di Medicina Intensiva, Ospedale Beata Vergine di Mendrisio, Switzerland.
authors.forename: Alberto
authors.initials: A
authors.lastname: Pagnamenta
authors.affiliation: Service de Médecine Préventive Hospitalière , CHUV, Lausanne, Switzerland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Francioli
authors.affiliation: Service de Médecine Préventive Hospitalière , CHUV, Lausanne, Switzerland.
authors.forename: Catherine
authors.initials: C
authors.lastname: Lazor-Blanchet
authors.affiliation: Service de Médecine Préventive Hospitalière , CHUV, Lausanne, Switzerland.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Zanetti
authors.affiliation: Swiss Lung Association, Berne, Switzerland.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Zellweger
mesh_terms: D000328:Adult; D000368:Aged; D016358:Contact Tracing / Q000379:methods*; D005260:Female; D006784:Hospitals, Teaching; D006801:Humans; D017757:Infectious Disease Transmission, Professional-to-Patient; D059425:Interferon-gamma Release Tests; D008297:Male; D008875:Middle Aged; D010564:Personnel, Hospital; D013557:Switzerland / Q000453:epidemiology; D014374:Tuberculin Test; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000453:epidemiology*