Correlation between tuberculin skin test and IGRAs with risk factors for the spread of infection in close contacts with sputum smear positive in pulmonary tuberculosis
1 Unitat de Tuberculosi de Drassanes, Hospital Universitari Vall d’Hebron, Barcelona, Spain
2 IDIAP Jordi Gol Research Foundation, Barcelona, Spain
3 Universitat Autònoma of Barcelona, Barcelona, Spain
4 Servei de Microbiologia, Institut d’Investigació Germans Trias i Pujol, Badalona, Spain
5 Servei de Pneumologia, Hospital Universitari Germans Trias i Pujol, Badalona, Spain
6 CIBER Enfermedades Respiratorias, Madrid, Spain
BMC Infectious Diseases 2014, 14:258 doi:10.1186/1471-2334-14-258Published: 13 May 2014
The aim of the study was to assess the correlation between the tuberculin skin test (TST) and in vitro interferon-gamma released assays (IGRAs) with risk factors for the spread of infection in smear positive pulmonary tuberculosis (TB) contacts.
We recruited prospective contacts with smear positive pulmonary TB cases. We looked at human immunodeficiency virus (HIV) infection and other conditions of immunosuppression, presence of BCG vaccination and the degree of exposure to the index case. Patients underwent the TST, chest radiography, sputum analysis when necessary, and IGRA assays (QFN-G-IT and T-SPOT.TB). Presence of cough, diagnostic delay (days between first symptoms and TB diagnostic), contact conditions: room size (square meters) and index of overcrowding (square meters per person) were investigated in the index case.
156 contacts (119 adults, 37 children) of 66 TB patients were enrolled, 2.4 (1-14) contacts per TB case. The positivity of the TST did not correlate with the risk factors studied: presence of cough (p = 0.929); delayed diagnosis (p = 0.244); room size (p = 0.462); overcrowding (p = 0.800). Both QFN-G-IT and T-SPOT.TB, showed significant association with cough (p = 0.001, and p = 0.007) and room size (p = 0.020, and p = 0.023), respectively.
Both IGRA associated better than TST with certain host-related risk factors involved in the transmission of disease, such as the presence of cough.