Role of Quantiferon-TB Gold Assays in Detecting Latent Tuberculous Infection among Contacts of Active Tuberculous Patients
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- Category: Vol. 79, June 2011
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Role of Quantiferon-TB Gold Assays in Detecting Latent Tuberculous Infection among Contacts of Active Tuberculous Patients,NARIMAN A. HELMY, SOMIA A. ESSA, AYMAN E. SALEM and HAMED A.H. TOAIMA
Abstract
The detection and treatment of latent tuberculosis (LTB) infection is a key strategy in the control of tuberculosis.
Conducting the present study aimed at evaluating the efficacy of Quantiferon TB Gold in detecting latent TB infection in close family contacts of active tuberculous patients in comparison to the tuberculin skin test.
This study was conducted on 91 cases; 31 males and 60 females. Tuberculin skin test (TST) was carried on 91 cases but 24 cases of those tested did not undergo a follow-up visit to read the diameter of the TST, so were considered lost subjects, while Quantiferon test (QFT) was carried on the same 91 cases, out of whom only 10 subjects had "indetermi-nate" results. So the available results for both tests refer only to 67 subjects out of the 91 who were included in the study. In 6 cases of these 67 subjects showed indeterminate results for Quantiferon. So actually we have comparable results for 61 cases from the 91 subjects. In the present study there was a statistically significant association between Quantiferon and Tuberculin tests.
Twenty seven subjects of individuals who have positive Tuberculin showed positive Quantiferon, and this number represents (44.2%) of all cases. Thirteen cases of individuals that have negative tuberculin showed negative Quantiferon, and this number represents (21.3%) of all cases. So concordant results were obtained in (65.5%) of the studied subjects and were not affected by gender or age. Discordant positive QFT reactions and negative TST reactions occurred in 7 cases of individuals that have negative tuberculin, and this number represents (11.5%) of all persons.
Discordant negative QFT reactions and positive tuberculin skin test reactions occurred in 14 cases of cases that have positive tuberculin, and this number represents (23%) of all persons. So discordant results were obtained in (34.4%) of the studied subjects and were not affected by gender or age.
The percentage of subjects with quantiferon positivity increased with accordance to the increase in the TST induration diameters.