Toxocariasis: critical analysis of serology in patients attending a public referral center for ophthalmology in Brazil.

Purpose: To analyze the contribution of IgG anti-Toxocara antibodies in the diagnosis of ocular toxocariasis (OT) in serum samples of patients attending a public referral center for ophthalmology in Brazil and to determine the most frequent ocular signs and symptoms.

Study Design: This was a retrospective descriptive study of a cohort of outpatients followed from December 1989 to May 2006.

Methods: IgG anti-Toxocara antibody titers were determined by enzyme-linked immunosorbent assay. The results were correlated with the clinical and funduscopic findings.

Results: Of the diagnoses for the 126 patients, 42 were considered as probable OT, 48 as negative, and 36 as inconclusive. The median IgG anti-Toxocara antibody titers of the patients with probable OT were significantly higher than those of the patients in the negative or inconclusive groups (P = 0.0001). Higher titers were observed more frequently in patients in the probable OT group (P = 0.01) than in the negative group, in which titers were absent or lower in most patients (P < 0.0001). The right eye was affected more in the OT group than in the negative group (P = 0.01), and inflammation was located mostly in the intermediate and posterior poles. The mean age of the patients diagnosed with probable OT was significantly lower (mean, 8 years) than that of the negative patients (mean, 14.5 years) (P = 0.006).

Conclusions: Higher levels of antibodies could help with the diagnosis of OT in patients with symptoms and clinical signs; however, negative results cannot exclude possible OT. Conversely, patients with negative serology or low titers make the diagnosis of OT less likely.