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J. Garweg, S.D. Garweg, F. Flueckiger, M. Boehnke; Sensitivity and Secifity of Detecting Local Production of Specific Antibodies of the IgG and IgA type in Active Ocular Toxoplasmosis . Invest. Ophthalmol. Vis. Sci. 2004;45(13):1673.
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Purpose: Due to an as yet not completely satisfying sensitivity of available diagnostic systems to confirm a local antibody production as diagnostic proof of the clinical diagnosis of ocular toxoplasmosis (OT), immunoblot analysis of specific bands present in the aqueous humour, but not the serum, and thereby demonstrating a local production of specific antibodies, has gained new interest. We therefore wished to address the question of sensitivity and specifity of this diagnostic method. Methods: Aqueous humour (AH) and serum were collected from 56 patients with active ocular toxoplasmosis at the time of first clinical presentation and submitted to immunoblot detection for the presence of a local production of specific antibodies of the IgG and IgA type. For this, stripes were equilibrated and exposed overnight at ambient temperature to the prediluted paired samples of AH (1:25) and serum (1:100) before hybridisation with AP–conjugated anti–human IgG and –IgA (dilution 1:500) and substrate reaction. For te calculation of sensitivity and specifity, controls derived from patients with uveitis of proven non–toxoplasmic origin (n=30) were included. The presence of single bands in AH, but not in serum, or at least three different markedly stronger bands within the AH than in serum, bound to antigens with a protein size of 20 – 80 kDA was defined to support a specific local antibody production. Results: A local production of specific antibodies of the IgG type was uncovered from 28/56 (50%) and one of specific IgA from 20/56 AH samples (33%) in active ocular toxoplasmosis, respectively, but also from each 5 control AH samles for IgG and IgA (17%) derived from patients with uveitis of confirmed non–toxoplasmic origin. From these data, detection sensitivities of 50% and 33% and specifities of each 83% for local production of antibodies of the IgG and IgA type, respectively, were calculated. Conclusions: Immunoblotting may well be used as a supportive diagnostic tool if other less expensive diagnostic tools failed to prove the diagnosis, if the as yet not satisfying specifity is respected in the interpretation of data. The sensitivity may be increased to 68% for the preic e of a reduced specifity (78%) by the combination of immunoblotting for specific IgG and IgA.
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