Antibody Testing in Patients With Neurological and Psychiatric Symptoms

The study found that patients with anti-GAD antibodies have high rates of epilepsy, cognitive dysfunction and type 1 diabetes (T1D).[1] They may also be less likely to have psychiatric symptoms compared with those without anti-GAD antibodies, but studies are inconsistent on this matter.

“From a clinical point of view, anti-GAD testing should be considered especially in patients with epilepsy of unknown origin with comorbidity of DM1 as well as cognitive complaints. Our study does not support extensive consideration in patients with psychiatric problems,” wrote lead author Rob Rouhl, MD, PhD, of Maastricht University Medical Center, (Maastricht, The Netherlands), and colleagues.

“From a clinical point of view, anti-GAD testing should be considered especially in patients with epilepsy of unknown origin with comorbidity of DM1 as well as cognitive complaints. Our study does not support extensive consideration in patients with psychiatric problems,” wrote lead author Rob Rouhl, MD, PhD, of Maastricht University Medical Center, (Maastricht, The Netherlands), and colleagues.

The decision about who to test for anti-GAD antibodies in routine clinical practice can be challenging. To shed more light on the issue, researchers reviewed the charts of 119 patients seen at two academic medical centers in The Netherlands between 2010 and 2014. The decision to test these patients for anti-GAD antibodies had been based solely on the presence of possible associated neurological and/or psychiatric symptoms. Fourteen percent (n = 17) of these patients had tested positive for anti-GAD antibodies.

• Characteristics of anti-GAD positive patients:
  Median age: 30 years
  All had epilepsy
  47% had cognitive dysfunction
• Significantly lower prevalence of psychiatric symptoms for anti-GAD positive vs anti-GAD negative (6% vs 33%, p = 0.021)
• Significantly more autoimmune comorbidities for anti-GAD positive vs anti-GAD negative (55% vs 9%, p<0.001)
   T1D most frequent comorbidity in anti-GAD positive vs anti-GAD negative (47% vs 1%) (p<0.001)

The authors noted that the results concerning psychiatric symptoms contradict a recent meta-analysis, which found a positive link between anti-GAD antibodies and psychosis.[2] Further research is needed to clarify the association between anti-GAD antibodies and psychiatric symptoms. The study included only patients from tertiary referral centers, in which the presence of anti-GAD antibodies may be higher than for a more diverse group.

• Study in The Netherlands found that patients with anti-GAD antibodies have high rates of epilepsy, cognitive dysfunction and T1D 
• Patients with anti-GAD antibodies were less likely to have psychiatric symptoms compared to those without anti-GAD antibodies, but studies are inconsistent on this matter
• Other evidence suggests a link between anti-GAD antibodies and psychosis; further studies are needed to clarify the link between anti-GAD antibodies and psychiatric symptoms
• Results could help clinicians decide which patients need anti-GAD antibody testing