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Open Access Research article

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

Maria Luiza de Souza-Galvão123*, Irene Latorre346, Neus Altet-Gómez12, María Ángeles Jiménez-Fuentes1, Celia Milà1, Jordi Solsona1, Maria Asunción Seminario1, Adela Cantos1, Juan Ruiz-Manzano356 and José Domínguez346

Author Affiliations

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

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BMC Infectious Diseases 2014, 14:258  doi:10.1186/1471-2334-14-258

Published: 13 May 2014

Abstract

Background

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.

Methods

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.

Results

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.

Conclusions

Both IGRA associated better than TST with certain host-related risk factors involved in the transmission of disease, such as the presence of cough.

Keywords:
Tuberculosis infection; Tuberculin skin test; Interferon gamma release assays; IGRA; Overcrowding; Diagnostic delay; Cough