Early aqueous humor analysis in patients with human ocular toxoplasmosis

To evaluate the diagnostic sensitivity of a panel of laboratory tests for o cular toxoplasmosis performed at the time of presentation, paired samples o f aqueous humor and serum were collected from 49 consecutive episodes of oc ular toxoplasmosis with a clinical course of less than 3 weeks. Total immun oglobulin G (IgG) and Toxoplasma gondii-specific IgG, IgM, and IgA were qua ntified by enzyme-linked immunosorbent assay. The avidity of T. gondii-spec ific IgG was determined, and DNA extracted from aqueous humor was amplified for detection of a glycoprotein B gene sequence of T. gondii. The diagnosi s was confirmed for 73% (36 of 49) of the patients; this rate rose to 79.5% if data from a later analysis of aqueous humor derived from five of the ne gative patients were included. The analysis of serum (detection of T. gondi i-specific IgM and analysis of consecutive serum samples) alone did not con tribute to the diagnosis. Calculation of local antibody production lacked d iagnostic sensitivity when it was determined less than 3 weeks after the ma nifestation of clinical symptoms (28 of 49 patients [57%]), but this rose t o 70% after an analysis of a second aqueous humor sample. The antibody avid ity index attained diagnostic significance in only 8 of 43 instances (19%), and T. gondii DNA was amplified from no more than 6 of 39 (16%) aqueous hu mor samples. However, T. gondii-specific IgA was found within the aqueous h umors of 11 of 43 patients (26%); measurement of the T. gondii-specific IgA level thus contributed substantially to the diagnostic sensitivity of the laboratory tests.