The prevalence of voltage-gated potassium channel (VGKC) and glutamic acid decarboxylase (GAD) autoantibodies in psychotic disorders: A systematic review and meta-analysis

Abstract

Introduction Antibodies to the voltage-gated potassium channel (VGKC) complex and glutamic acid decarboxylase (GAD) have been reported in some cases of psychosis. We conducted the first systematic review on VGKC and GAD, and meta-analysis on GAD, to investigate their prevalence in people with psychosis. Objectives The objective was to examine the available evidence to determine the prevalence of serum VGKC and GAD antibody positivity in psychosis. Aims To search the available literature for data indicating the prevalence of these antibodies in psychosis. If data were sufficient, we anticipated conducting a meta-analysis. Methods Two authors searched major electronic databases for studies reporting the prevalence of VGKC and GAD65 antibody seropositivity in psychotic disorders. We then conducted a random effects analysis with Comprehensive Meta-Analysis software (CMA, Version 3). Results Only three studies presenting prevalence rates of VGKC sero-positivity in psychosis could be identified, with an overall prevalence of 0.5% (1/196) with to 0% in healthy controls (0/50). Meta-analysis established the pooled prevalence of GAD65 autoantibodies was 8.67% (95% CI 3.9–17.80%, I 2 =75%, 8 studies) in psychotic disorders. People with psychosis were more likely to have GAD65 antibodies than controls (OR 3.14 95% CI 1.55–6.37%, P =0.001, 7 studies, I 2 =0%). Conclusions Rates of VGKC antibody positivity appear to be low in psychosis, although there is a lack of published evidence. The prevalence of GAD65 antibodies is higher but available studies did not control for the presence of T1 diabetes, a condition in which GAD65 antibodies are also found.