Diagnostic delay as main contributing factor to a large outbreak of tuberculosis in a university. / Demora diagnóstica como principal factor contribuyente a un importante brote de tuberculosis en una universidad.

OBJECTIVE: To describe the epidemiological characteristics of a large tuberculosis outbreak in the university environment and the main risk factors associated with it. METHOD: A descriptive analysis of the data collected from sick individuals and their contacts was made. For the contact tracing, the guidelines established in the Tuberculosis Programme of the Autonomous Community of the Basque Country were followed. Six of the outbreak strains were sent to the National Centre of Microbiology for molecular typing. RESULTS: The total number of cases of the outbreak was 11. The rate of tuberculosis infection in the classroom of the index case, including the sick individuals, was 88.1% (59 infected and only 8 uninfected). The diagnostic delay of the index case was 260 days, and in the other 8 symptomatic cases it ranged between 10 and 70 days. The pattern obtained by the 2genotyping techniques was identical in the 6 strains studied. CONCLUSIONS: The long diagnostic delay of the authentic index case, which was diagnosed in the contact tracing, and the poor ventilation conditions of the classroom, determined the high number of secondary cases associated with this outbreak.

[Comparative performance of QuantiFERON(®)-TB Gold IT versus tuberculin skin test among contact investigations for latent tuberculosis infection]. / Estudio comparativo de QuantiFERON(®)-TB Gold IT frente a tuberculina para el diagnóstico de la infección tuberculosa latente en estudios de contactos.

BACKGROUND AND OBJECTIVE: Until recently, the only tool for detection of latent tuberculosis infection (LTI) was the tuberculin skin test (PPD). QuantiFERON(®)-TB Gold In-Tube (QF), as well as other Mycobacterium tuberculosis-specific interferon-γ release assays (IGRAs), appears to be an alternative or adjunct to the PPD. The goal of the study was to compare QF with PPD to evaluate de accuracy of QF for routinely identifying LTI in contact investigations. PATIENTS AND METHOD: We performed a descriptive and prospective study with contacts of culture-confirmed tuberculosis source cases in Bizkaia and Araba from May 2007 through February 2008 who underwent QF and PPD. Concordance between both tests was analyzed using the kappa statistic (κ). RESULTS: 376 contacts were found: 8 were high-risk children (age < 15), 30 low-medium risk children, 46 high-risk adults (age>14) and 270 low-medium risk adults. PPD was positive in 160 subjects (42.5%) at PPD ≥ 5mm, 141 (37.5%) at PPD ≥ 10mm and 95 (25.3%) at PPD ≥ 15 mm. In QF analysis 94 subjects were positive, 279 negative and 3 indeterminate. Overall agreement between QF and PPD was good at PPD ≥ 10mm (κ=0.53; p<0.0001) but agreement was poor when the index case had positive baciloscopy at PPD ≥ 5mm (κ=0.28; p<0.001) and high-risk contacts at PPD ≥ 15 mm (κ=0.048; p=0.36). CONCLUSIONS: IGRAs are an accurate indicator of LTI, providing a more specific way of diagnostic and reducing the number of subjects to be treated. QF appears to be a valuable public health tool with potential advantages over the PPD and improving resources.