title: The role of the interferon gamma release assay in assessing recent tuberculosis transmission in a hospital incident.
abstract: In 2007, an extensive contact screening investigation into onward transmission of tuberculosis was instigated at a hospital in Northern Ireland following diagnosis of pulmonary multi-drug resistant TB in a healthcare worker. Interferon gamma release assays (IGRAs) were used to test 333 patients and 98 staff. We investigated for evidence of onward transmission and recent infection based on analysis of clinical, demographic and IGRA data. We also described within-patient variability of IGRA results. Among patients and staff, increasing age of patients was the only factor associated with IGRA positivity. Greatest within-subject variability of IU/mL in serially-tested patients/staff was seen in those with a positive IGRA test and this did not correlate with increased exposure to the index case. IGRA positivity being largely explained by increasing age in patients and previous TB contact in staff lends weight to the conclusion that IGRA positivity reflected previous infection rather than recent transmission.
authors.affiliation: Tuberculosis Section, Respiratory Diseases Department, Health Protection Agency Centre for Infections, London, England. louise.bradshaw@hpa.org.uk
authors.forename: Louise
authors.initials: L
authors.lastname: Bradshaw
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Davies
authors.forename: Michael
authors.initials: M
authors.lastname: Devine
authors.forename: Peter
authors.initials: P
authors.lastname: Flanagan
authors.forename: Paul
authors.initials: P
authors.lastname: Kelly
authors.forename: Kevin
authors.initials: K
authors.lastname: O'Connor
authors.forename: Francis
authors.initials: F
authors.lastname: Drobniewski
authors.forename: Vladislav
authors.initials: V
authors.lastname: Nikolayevskyy
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Abubakar
mesh_terms: D000328:Adult; D003710:Demography; D005260:Female; D005500:Follow-Up Studies; D006282:Health Personnel; D006761:Hospitals; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007371:Interferon-gamma / Q000378:metabolism*; D055985:Latent Tuberculosis / Q000635:transmission; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D016017:Odds Ratio; D014376:Tuberculosis / Q000635:transmission*
chemical_list: D007371:Interferon-gamma