Introduction: Group A Beta-Hemolytic Streptococcus (GABHS) can induce PANDAS (pediatric autoimmune neuropsychiatric disorders associated with streptococcal infection). GABHS is the most important and common bacterial cause of acute pharyngitis in Iranian children. We studied the role of GABHS (anti-streptococcal antibodies) in suspected cases of PANDAS in a cross sectional studies. Methods: Across sectional study was done in 2 pediatric psychiatric/and neurologic clinics in Tehran (Rasul Akram and Aliasghar Hospital) during 2008-2010. We studied serum antistreptococcal antibodies (anti streptolysin O, anti Deoxyribonuclease B, and anti-streptokinase (ABcam-ELISA, USA) in 76 cases with psychiatric manifestation (OCD, ADHD) in compare with 39 healthy controls. These antibodies were studied in 53 cases with movement disorders (Tic/Tourette syndrome) in compare with 76 healthy controls. Sensitivity, specificity and positive predictive value of tests were calculated. Results: In movement disorders ASOT, Anti-DNase and Anti streptokinase was significantly higher than controls (p 200IU/ml) had 75 sensitivity; 84 specificity and 80 PPV; Antistreptokinase (cut off level> 332 IU/ml) had 34 sensitivity; 85 specificity, and 72 PPV; Anti-DNase (cut off level> 140IU/ml) had 70 sensitivity; 99 specificity and PPV 90 for differentiating the group. ASOT, Anti-DNase and Anti streptokinase titer was significantly higher than controls (p<0.0001, p=0.000, p<0.0001). ASOT had 90 sensitivity; 82 specificity, PPV 92; Anti streptokinase: 82 sensitivity; 82 specificity, PPV 95; Anti DNase: 92 sensitivity; 82 specificity, PPV 92 for differentiation the cases from normal controls. Discussion: These findings support that a post infectious immune mechanism to GABHS may play a role in the pathogenesis of PANDAS in our children. A combination of throat culture, rapid antigen detection test, and serologic testing for GABHS is required to achieve maximum sensitivity and specificity for diagnosis. We prefer to use antibiotic prophylaxis in PANDAS cases for preventing recurrent streptococcal infections. Ongoing research is needed for identifying optimum diagnostic, prevention and therapeutic approach especially, aggressive treatment (intravenous immunoglobulin, plasmaphresis)
