RESUMO
Objective: This study was designed to ascertain the diagnosis of active human ocular toxoplasmosis by detection of local anti-Toxoplasma IgA,IgM and IgG, as well as Toxo IgG avidity in tear samples
Subjects and methods: Patients attending the Outpatient Clinic of Ophthalmology Department-Tanta University Hospital during the period from April 2005 to June 2006 were examined and those suspected to have ocular lesions compatible with ocular toxoplasmosis were selected. The patients were classified into two groups: Group [I]: 14 patients with signs of active posterior uveitis presumably due to toxoplasmosis [APUPT]. Group [II]: 26 patients with chronic retinochoroidal lesion without active uveitis. A third group of 20 healthy individuals were chosen as a control group [group III]. Tears and serum samples were collected and were investigated for anti-Toxoplasma IgA, IgM and IgG. The positive samples for anti-Toxoplasma IgG were further investigated for Toxo-IgG avidity
Results: Regarding group [I] with APUPT, It was found that the tears of 9 out of 14 examined patients [64%] showed secretory IgA [sIgA]. In addition, 10 out of 14 patients [71%] had positive IgG values in their tears, nine of them had low avidity IgG, with only one patient had high avidity IgG. The simultaneous presence of sIgA and low avidity IgG in the tears denoted recent active infection. The serum samples showed the detection of IgA in 5 patients [36%] and IgG in 8 patients[57%]. In group II, sIgA could be detected in tear samples of 2 out of 26 patients [8%], whereas 19 patients [73%] had positive IgG values that all were high avidity. In serum samples, there were 3 patients[12%] with positive IgA, while 21 patients [81%] had positive IgG that all had high avidity. In the control group [III], only one subject out of 20 controls [5%] had IgA in both tear and serum samples. There were 4 and 7 patients [20% and 35%] presenting IgG in tear and serum samples respectively. All IgG had high avidity in both tear and serum samples. Anti-Toxoplasma IgM antibodies were not detected in any of tear or serum samples of all subjects in all groups
Conclusion: From this study it can be concluded that the simultaneous detection of anti-Toxoplasma sIgA and low avidity IgG in tear samples could be considered as a useful marker for early diagnosis of active ocular toxoplasmosis .Moreover, the tear fluid can be considered as a promising candidate for detection of local ocular antibodies because its collection is simple, easy and noninvasive