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R. Gineys, S. Trad, N. Cassoux, C. Terrada, C. Fardeau, P. Lehoang, B. Bodaghi; Quantiferon-tb Gold in Uveitis:Quantitative Results. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1545.
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To evaluate the cut-off value of QuantiFERON-TB Gold test (an interferon-gamma release assay) in the diagnosis of tuberculous uveitis. Bacteriological proof is seldom available from ocular fluids analysis in so-called tuberculous uveitis, the diagnosis of which relies mainly on indirect evidence of a contact with Mycobacterium tuberculosis. QuantiFERON-TB Gold is a very specific test which has not yet been fully investigated in ophthalmology.
In the setting of ancillary testing for uveitis, QuantiFERON-TB Gold test was performed in 96 patients referred between January and October 2007 to the Ophthalmology department of the Pitie-Salpetriere Hospital, Paris. An antituberculous treatment was initiated based on clinical features and the results of the work-up. ROC curve analysis was applied to the numeric value of the test in each group (positive and negative therapeutic test), to assess a more meaningful positive threshold.
Forty-two out of 96 patients (43.7%) had a positive QuantiFERON-TB Gold test but an anti-TB regimen was performed in 25 patients (26%). Fifteen patients (60%) had a positive therapeutic test, six of which also were on systemic corticosteroids. QuantiFERON-TB Gold median value in those with a positive therapeutic test was 7.67 UI/ml (0.46 to 33.37 UI/ml) whereas the median value in those with a negative therapeutic test was 1.22 UI/ml (0,61 to 4.4 UI/ml). Those results suggest a positive cut-off value of 2 UI/ml for the QuantiFERON-TB Gold test, as a meaningful threshold to decide which patients would better benefit from an antituberculous treatment, with a specificity of 87% and a sensibitivity of 84%.
The current cut-off value given by the laboratory for QuantiFERON-TB Gold test positivity does not discriminate between an active TB infection and a mere immunological scar. Our results are in agreement with those of the literature suggesting the need for a thorough evaluation of the cut-off value of this test that would be the more suitable for therapeutic decision making.
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