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This abstract is assigned to session RAPPORT - BOG: Belgisch Oftalmologisch Gezelschap / SBO: Société Belge d'Ophtalmologie

Title

Tuberculosis in areas of low prevalence

Purpose	The diagnosis of intraocular tuberculosis is difficult due to the large variations in clinical presentations, lack of uniformity in diagnostic criteria, and the low yield of organisms from the eye. It is generally based on the association of compatible ophthalmological signs and evidences of systemic infection. Since tuberculosis uveitis is usually found in the latent form of the infection, its diagnosis relies on the analysis of systemic tuberculosis immunity. Nowadays, two diagnostic tests are available: the tuberculin skin test (TST) and the interferon gamma release assays (IGRAs: Quantiferon and T.spot.TB).
Methods	As for every screening test, disease prevalence will greatly influence their correct interpretation. Hence, a good screening test will have a good positive predictive value in a population where the disease have a high prevalence and a bad positive predictive value in a low prevalence context. The prevalence in Belgium has progressively decreased during the 20th century and in 2007 the incidence was below 10 cases/100000 inhabitants.
Results	However the distribution is different in the three main region of the country, and is particularly high in Bruxelles where the incidence is around 30 cases/100000 inhabitants/year. This is partially due to the important population of immigrants from high prevalence area, found in the capital.
Conclusion	In this perspective, the interpretation of TST and IGRAs is particularly difficult and the diagnosis of tuberculosis uveitis must be made with caution.

Author 1

Last name	WILLERMAIN
Initials	F
Department	Ophthalmology CHU St-Pierre and Brugmann
City	Brussels