Comparison of QuantiFERON TB Gold with tuberculin skin test for the diagnosis of tuberculosis infection in risk groups

Abstract number: P1834

Perez-Escolano E., Gutierrez-Rodriguez J., Menor E.M., Alados J.C., López M.I., De Tena S., López-Prieto M.D.

Objective: To evaluate the agreement of the QuantiFERON® TB Gold In Tube test (QFT) and the tuberculin skin test (TST) for the diagnosis of tuberculosis infection (TBI) in risk groups (RG), and to establish the utility of QFT as a tool for the indication of TBI treatment.

Methods: We studied 409 immunocompetent persons who came for screening of tuberculosis infection; average age was 41 years (SD: 14.8), 79% were men and 263 (65.4%) had been vaccinated with BCG. All were screened with chest X-ray, TST, QFT (Cellestis, Australia) and risk factors were registered in a questionnaire. TST was performed by Mantoux method and a positive test was defined as an induration geqslant R: gt-or-equal, slanted5 mm in non-vaccinated and geqslant R: gt-or-equal, slanted15 mm in vaccinated people. QTF was made according to the manufacturer specifications. We considered as vaccinated persons those presenting with a suggestive scar. CDC recommendations were followed for the interpretation of the QFT and the treatment of the TBI. Agreement between TST and QFT was assessed by the Cohen kappa coefficient.

Results: Agreement between the TST and the QFT was 78.7% (Kappa 0.51, CI (0.36–0.65)) among non-vaccinated population. In the vaccinated group, agreement was smaller (69.6%, Kappa 0.38, CI (0.27–0.49). QTF(-)/TST(+) was the most frequently detected discordant result for the non-vaccinated group. Whereas, for vaccinated people, rate of QTF(+)/TST(-) results and QTF(-)/TST(+) results were similar. TST was positive in 107/136 non-vaccinated people, from these 26 were negative for QTF. In the vaccinated group, 120/263 were TST positive, from these 46 were negative for QTF. The indication of TBI treatment made by TST and risk situation was modified in 42% of cases according to QFT test. We prescribed treatment of TBI by QFT in 25% of the patients that did not have indication according to the TST.

Conclusions: Agreement between TST and QFT was low in vaccinated people, even thought TST was considered positive for 15 mm. Whereas, in non-vaccinated people the agreement was moderate. The use of QFT allows for a better selection of infected individuals and to reduce the number of unnecessary treatment of TBI.

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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