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Studies Of The Relationship of GAS to Tic Disorders

(Including Episodic Tic Disorders Labeled as PANDAS)

Reference Findings/ Critique
[Leckman2011] Streptococcal upper respiratory tract infections and exacerbations of tic and obsessive-compulsive symptoms: a prospective longitudinal study.
Findings: (N=31, C=53). Children were monitored on monthly basis for 25 months to determine if there was a correlation between a positive GABHS infection (rise of titers and positive throat culture) and symptom exacerbation. Subjects and controls had very similar rates of tic and/or OCsymptom exacerbations. Rates of GABHS infection were likewise similar between subjects and controls.
Critique: Primary author states that he does not believe there were any true PANDAS cases in the study after seeing later examples of PANDAS cases. The authors note that severity of exacerbations in the subjects did not match published reports of sawtooth like response in PANDAS subjects. This raising questions whether the selection criteria were sufficient to properly select intended subjects. Authors recommend tightening the criteria to ensure a coherent group of subjects.
[Schrag2010] Streptococcal infection, Tourette syndrome and OCD: Is there a connection?
Findings: (N=255, C=4519) Authors retrospectively sampled a large medical database in the UK to see whether a preceding infection led to a higher likelihood of a diagnosis of OCD or TS. Incident rates of OCD and TS matched preceding literature. Laboratory data in support of GABHS infection was largely missing with only 67 throat swabs and 6 ASO titers in the entire database. The authors used a wide set of diagnostic codes to look for a possible correlation. Conclusion was that subjects did not differ strongly from controls when seeking whether a preceding infection was correlated with a diagnosis of OCD or TS.
Critique:While the paper is interesting for confirming the incidence of TS and OCD, the diagnostic codes used for determining a possible streptococcal infection were quite broad and included sore throats to Acute staphylococcal tonsillitis. It is unlikely that any claims can be made regarding streptococcal infections with the extremely broad selection criteria and lack of laboratory confirmation.
[Bombaci2009] Protein array profiling of tic patients sera reveals a broad range of enhanced immune response against Group A Streptococcus antigens.
Findings: (n=61, c=35, n=239) 61 kids had tics and neurological issues, 35 kids had no strep and no tics, and 239 kids had strep. Their blood was exposed to 102 proteins of Group A Strep. 33% of the tic patients reacted very intensely to 30% of the strep proteins while only 12% of strep kids & 1% of control kids reacted similarly. 21 antigens solicited a stronger response in tic patients than strep only patients and 5 of the strep proteins solicited a response from the tic only group, even they did not have a strep infection. This study provides evidence that tic patient sera from kids who did not have an active strep infection exhibits immunological profiles similar to and in some cases more robust than individuals who have a current strep infection.
[Morris2009] Serum autoantibodies measured by immunofluorescence confirm a failure to differentiate PANDAS and Tourette syndrome from controls
Findings: (N=30 TS,30 PANDAS, C=30)
No significant differences in immunofluorescence or localization were identified in patients with PANDAS (n=30) and TS (n=30) as compared to controls (n=30). Further comparisons showed no correlation between autoreactivity determined by immunofluorescence and the presence of previously measured immunoblot reactivity against human caudate or putative antigens (pyruvate kinase M1 and aldolase C). These results confirm an inability to distinguish patient populations by antibody measurements and raise further concerns about the presence of an autoimmune mechanism in PANDAS and TS.
Critique: It is unclear if the samples for PANDAS were drawn during symptom exacerbation.
[Gause2009] Antineuronal antibodies in OCD: comparison in children with OCD-only, OCD+chronic tics, and OCD+“PANDAS”
Findings: (N=13,20,23, C=29). ELISA and immunohistochemistry showed no differences amongst groups of OCD-only, OCD+PANDAS, OCD+Chronic Tic Disoder. Immunoblot showed that a greater percentage of individuals in the OCD+PANDAS cohort had reactive bands at 27 kDa (caudate, cingulate gyrus, dorsolateral prefrontal cortex), 36 kDA (caudate), 100 kDa (orbitofrontal, caudate) and increased peak height at 67 kDa (all regions). Immunoblotting studies using the Stu antigens (pyruvate kinase M1, aldolase C, alpha- and gamma-enolase) did not differ among groups. ASO titers were similar in all groups and did not correlate with immunoassays.
Critique: Samples for PANDAS group were drawn from [Kurlan2008] longitudinal study where children met the1998 criteria for PANDAS but did not exhibit the expected change in symptoms at exacerbations (i.e., almost no change in OCD symptoms over a 2 year period). In addition, samples were from children with long-standing Tourette’s Syndrome rather than the sentinel event. Subsequent papers have recommended tightening the selection criteria to ensure a coherent cohort.
[Morer2008] Antineuronal antibodies in a group of children with obsessive-compulsive disorder and Tourette syndrome
Findings: (N=53, C=19) Antibodies were assayed by immunohistochemistry and immunoblot. No anti-basal ganglia antibodies were detected by immunohistochemistry. Two proteins with weights of 86kDa and 55 kDa were found in sera from 7 patients. Though the study supports the hypothesis of an autoimmune process underlying OCD or TS in some patients, further research is needed.
Critique: Sample is small and strength of correlation light.
[Singer2008] Serial immune markers do not correlate with clinical exacerbations in pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections
Findings: (N=12) Serum was drawn from twelve patients in the [Kurlan2008] longitudinal study to determine if antibodies against human postmortem caudate, putamen and prefrontal cortex were correlated with exacerbations. No correlation was found.
Critique: Unclear what conclusion to draw from this paper. The samples in this study comes from the Kurlan 2008 longitudinal study where patients did not have a clinical presentation consistent with PANDAS literature and lead author questions if there were true PANDAS cases. Subsequent papers have recommended tightening the selection criteria to ensure PANDAS subjects are actually selected.
[Kurlan2008] Streptococcal infection and exacerbations of childhood tics and obsessive-compulsive symptoms: a prospective blinded cohort study
Findings: (N=40, C=40) Compared TS/long-term tic patients who met PANDAS criteria to TS patients who did not (controls).  Forty children with tics (95%), or comorbid tics+OCD (56%) or OCD-only(5%) were followed for 2 years to determine whether their exacerbations were temporally correlated with GABHS infections. Authors note that while their subjects met the criteria for PANDAS, they had a different clinical presentation than reported in the literature. Course and severity at exacerbations were similar between subjects and control with almost no change in OCD symptoms over a 2 year period. There was a surprisingly low number of GABHS infections in subjects and controls with subjects being twice as likely to have a positive culture for GABHS and three times as likely to have a probable GAS infection. Authors concluded that children meeting the PANDAS criteria seem more likely to get GAS infection and there was no statistical difference in exacerbations due to strep between TS patients meeting the PANDAS criteria & TS controls.
Critique: Study did not look at onset of symptoms in the selection process and authors note that subjects appeared clinically different than described PANDAS patients (no OCD exacerbations in 2 years, no comorbidities).  This difference in clinical presentation raising the question whether the PANDAS selection criteria was sufficiently clear to separate patients (despite  2004 clarification) and whether it was correctly applied. Exacerbations in comorbidities were not tracked.