Diagnostic value of polymerase chain reaction in blood and aqueous humor in immunocompetent patients with ocular toxoplasmosis

Purpose: To evaluate the diagnostic value of polymerase chain reaction (PCR ) in blood and aqueous humor samples from immunocompetent patients with rea ctivated ocular toxoplasmosis. Methods: Group 1 was composed of seven patients with a clinical diagnosis o f reactivated ocular toxoplasmosis. Group 2 consisted of 33 controls. In ea ch subject, blood and aqueous humor samples were obtained for detection of Toxoplasma gondii DNA by means of simple PCR, seminested PCR, and Southern blot hybridization. Results: Group 1: Simple PCR was positive in 3 of 7 blood samples (42%) and in 2 of 7 (28%) aqueous humor samples. Seminested PCR was positive in 4 of 7 (57%) blood samples and in 3 of 7 (42%) aqueous humor samples. Group 2: Simple and seminested PCR were positive in both samples in 2 of 33 (6%) and 4 of 33 (12%), respectively. Sensitivity 57% (18.41-90.10), specificity 87 % (71.80-96.60); positive and negative likelihood ratio 4.38 and 0.49, resp ectively. Conclusions: Polymerase chain reaction can be useful for confirming the dia gnosis of ocular toxoplasmosis, especially in those eyes where fundus exami nation does not yield conclusive results. The detection of T gondii DNA in blood suggests that reactivation of ocular toxoplasmosis cannot be consider ed a local event.