Anti-GAD antibodies in a cohort of neuropsychiatric patients

Abstract

Objective: Antiglutamate decarboxylase (anti-GAD) antibodies are associated with several neurological manifestations, like epilepsy and movement disorders. However, in daily neurological practice, it remains hard to define when to test for anti-GAD antibodies in patients with neurologic and/or psychiatric symptoms. Therefore, here, we report the patient characteristics of a large retrospective cohort of patients tested for anti-GAD antibodies in clinical practice and compare the characteristics of anti-GAD positive and anti-GAD negative patients.

Methods: We blindly assessed relevant clinical symptoms and comorbidities and functional outcome with the modified Rankin Scale (mRS) in a retrospective observational cohort of all patients in which the decision to assess anti-GAD levels had been made based solely on the presence of possible associated neurological and/or psychiatric symptoms (N=119).

Results: Out of 119 patients, 17 (14.3%) were anti-GAD positive. The anti-GAD positive patients had a median age of 30years (range: 3-64; 2 children). They all had epilepsy, with 8 (47%) patients reporting cognitive complaints. Psychiatric symptoms were less prevalent in anti-GAD positive patients, only 1 anti-GAD positive patient (6%) versus 34 anti-GAD negative patients (33%) reported psychiatric symptoms (p=0.021). The most frequent comorbidity of anti-GAD positive patients was diabetes mellitus type 1 (n=8). Twelve (71%) and 13 (78%) of the anti-GAD positive patients were functionally independent at the time of diagnosis and after one year, respectively (mRS score: 0 to 2). There was no significant difference in functional status at any time during follow-up compared with the anti-GAD negative group.

Conclusion: Antiglutamate decarboxylase (anti-GAD) antibodies relate to epilepsy with or without cognitive complaints. However, psychiatric symptoms were almost absent in anti-GAD positive patients, and the presence of anti-GAD antibodies contributed little to the prognosis in our cohort.

Keywords: Anti-GAD; Antibodies; Autoimmune encephalitis; Glutamate decarboxylase; Neuropsychiatric syndromes; Refractory epilepsy.