A prospective study was conducted of 865 patients with uveitis to determine the frequency of associated systemic diseases and to assess the value of limited laboratory screening of these patients. All patients underwent a standard diagnostic protocol followed -when indicated -by special tests and procedures performed in order of likelihood ('tailored approach'). For 628 patients (73%) a specific diagnosis was established based on history, ophthalmologic examination, and laboratory and radiographic studies. A definite association with systemic disease was determined for 220 patients (26%). A relationship with a subclinical systemic disorder could be presumed in 201 cases (23%) and a well-established clinical uveitis entity without a recognisable systemic disorder was present in 207 cases (24%). For 237 patients (27%) a diagnosis could not be determined. The most frequently observed systemic diseases were sarcoidosis (7%) and HLA-B27-associated seronegative spondylarthropathies (6%). Presumed or definite toxoplasmosis was encountered in 10% of cases. HLA-B27-associated acute anterior uveitis was the most common clinical entity (17%). In the majority of cases the presence of a systemic disease was not suspected prior to eye involvement and was only recognised after the subsequent diagnostic procedures.

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Analysis of local toxoplasma antibody production to confirm a suspected clinical diagnosis of toxoplasma chorioretinitis is a valuable diagnostic tool. Determination of toxoplasma antibodies in the blood of the patient is of limited use. When blood toxoplasma tests are negative this indicates that toxoplasma as a causative organisms in the pathogenesis of uveitis is unlikely. A positive blood test is a sensitive test (100% patients positive) but not a specific test since so many healthy individuals already have undergone subclinical infection and have acquired humoral immunity against the parasite. We analysed 93 paired aqueous and serum samples for toxoplasma antibodies and total IgG and determined the Goldmann-Wittmer coefficient. In patients retrospectively diagnosed as having toxoplasma chorioretinitis 16 out of 22 had a positive coefficient, indicating local parasite antibody production. In one patient with AIDS we also found a positive toxoplasma coefficient. Three out of 15 patients with posterior uveitis of unknown origin also had a positive coefficient. None of the cataract patients tested (n = 32) had a positive coefficient. Major drawbacks of aqueous humor analysis are that a false negative antibody coefficient can occur when a massive blood aqueous barrier breakdown has occurred.

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