BACKGROUND: Interferon-gamma (IFN-gamma) release assays (IGRAs), such as the QuantiFERON-TB Gold In-Tube test (QFT-GIT), are becoming a preferred method for diagnosis of tuberculosis (TB) infection in many industrialised countries. However, data on the effectiveness of IGRAs in high TB-HIV (human immunodeficiency virus) endemic and resource-limited settings, such as Zambia, are limited. OBJECTIVE: To determine the intra-assay reliability and robustness of QFT-GIT in a field setting in Zambia. DESIGN: During July-October 2007, 109 adult smear-positive TB patients were recruited to determine QFT-GIT reliability and the effect of a 24-h delay in incubation. Two simulated laboratory experiments were also performed using 9-14 volunteers, to explore the effect of power outages during incubation and storage temperature of collection tubes on IFN-gamma responses. RESULTS: QFT-GIT intra-assay concordance was 91.7% (kappa = 0.8). Discordance was observed for nine patients, of whom six were HIV-positive. There was evidence of an association between HIV status and discordant results (OR 1.98, 95%CI 1.06-3.67, P = 0.03). A 24-h delay in incubation changed results for 25 of the 109 (22.9%) patients. Power outages that altered incubation time reduced IFN-gamma responses. CONCLUSION: Although QFT-GIT seems reliable in this setting, we have identified operational factors that affect its robustness. These factors may influence the effectiveness of this test in similar resource-limited settings.
BACKGROUND:Interferon-gamma (IFN-gamma) release assays (IGRAs), such as the QuantiFERON-TB Gold In-Tube test (QFT-GIT), are becoming a preferred method for diagnosis of tuberculosis (TB) infection in many industrialised countries. However, data on the effectiveness of IGRAs in high TB-HIV (human immunodeficiency virus) endemic and resource-limited settings, such as Zambia, are limited. OBJECTIVE: To determine the intra-assay reliability and robustness of QFT-GIT in a field setting in Zambia. DESIGN: During July-October 2007, 109 adult smear-positive TB patients were recruited to determine QFT-GIT reliability and the effect of a 24-h delay in incubation. Two simulated laboratory experiments were also performed using 9-14 volunteers, to explore the effect of power outages during incubation and storage temperature of collection tubes on IFN-gamma responses. RESULTS: QFT-GIT intra-assay concordance was 91.7% (kappa = 0.8). Discordance was observed for nine patients, of whom six were HIV-positive. There was evidence of an association between HIV status and discordant results (OR 1.98, 95%CI 1.06-3.67, P = 0.03). A 24-h delay in incubation changed results for 25 of the 109 (22.9%) patients. Power outages that altered incubation time reduced IFN-gamma responses. CONCLUSION: Although QFT-GIT seems reliable in this setting, we have identified operational factors that affect its robustness. These factors may influence the effectiveness of this test in similar resource-limited settings.
Authors: Elisa Nemes; Virginie Rozot; Hennie Geldenhuys; Nicole Bilek; Simbarashe Mabwe; Deborah Abrahams; Lebohang Makhethe; Mzwandile Erasmus; Alana Keyser; Asma Toefy; Yolundi Cloete; Frances Ratangee; Thomas Blauenfeldt; Morten Ruhwald; Gerhard Walzl; Bronwyn Smith; Andre G Loxton; Willem A Hanekom; Jason R Andrews; Maria D Lempicki; Ruth Ellis; Ann M Ginsberg; Mark Hatherill; Thomas J Scriba Journal: Am J Respir Crit Care Med Date: 2017-09-01 Impact factor: 21.405
Authors: Jason R Andrews; Mark Hatherill; Hassan Mahomed; Willem A Hanekom; Monica Campo; Thomas R Hawn; Robin Wood; Thomas J Scriba Journal: Am J Respir Crit Care Med Date: 2015-03-01 Impact factor: 21.405
Authors: Saloua Tagmouti; Madeline Slater; Andrea Benedetti; Sandra V Kik; Niaz Banaei; Adithya Cattamanchi; John Metcalfe; David Dowdy; Richard van Zyl Smit; Nandini Dendukuri; Madhukar Pai; Claudia Denkinger Journal: Ann Am Thorac Soc Date: 2014-10
Authors: Madhukar Pai; Claudia M Denkinger; Sandra V Kik; Molebogeng X Rangaka; Alice Zwerling; Olivia Oxlade; John Z Metcalfe; Adithya Cattamanchi; David W Dowdy; Keertan Dheda; Niaz Banaei Journal: Clin Microbiol Rev Date: 2014-01 Impact factor: 26.132