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J Garweg, F Flückiger, P Jacquier; Results Of Second Aqueous Humor Analysis in Primarily Not Confirmed Human Ocular Toxoplasmosis . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4302.
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Purpose:A local production of specific antibodies may be detected in 50 to 75% of cases from paired aqueous humor and serum samples calculating the C value. The diagnosis in the remaining cases may be wrong, or immunological phenomena may account for the failure to detect local antibodies in the aqueous humor, i.e. antibody consumption or late onset antibody production. The current study addresses this aspect. Methods:Paired aqueous humor and serum samples were collected from a subset of 19 consecutive patients with a typical clinical picture of ocular toxoplasmosis at the time diagnosis and 2 - 26 weeks thereafter who had either no specific aqueous antibodies detectable at first presentation (n = 13) or a second puncture for other purposes (i.e. intraocular surgery required; n = 6) after informed consent had been given. From all samples, specific antibodies as well as the whole IgG and IgA fraction were quantified, additionally parasite DNA amplified from the aqueous humor sediments. Results:An indicative or confirmative C value was calculated in 5/19 (0/13 and 5/6) cases at diagnosis and in 9/19 (3/13 and 6/6) after a second puncture with an average increase in C values from 9.5 to 64. Specific IgA was primarily detected in 2 cases and found at second puncture in 3 cases. 6 samples tested positive for parasite DNA, four of these from patients with no specific aqueous antibodies detectable. Conclusion:In cases with clinically less prominent inflammatory changes, anti-Toxoplasma antibodies may be detected markedly after first clinical symptoms. This may be attributed to a delayed onset of local antibody production, or antibody consumption being responsible for falsely negative results at early aqueous humor analysis. Therefore, aqueous humour antibody analysis may be used only late to establish the clinical diagnosis using laboratory measures, early aqueous humor antibody analysis should not account for clinical decision making.
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