Methods, assays, and apparatus are disclosed for testing of antigens associated with intestinal and/or blood-brain barrier permeability. For example, blood, saliva or other bodily fluid can be tested for binding (1) to a bacterial toxin (preferably a lipopolysaccharide), and (2) binding to tissue antigens selected from at least one of (a) a gut-related antigen and (b) a blood brain barrier-related antigen. Analysis of test results can be used to assist in detecting and diagnosing diseases associated with leaky gut syndrome (whether due to paracellular or transcellular pathways, and whether due to bacterial toxins or some other cause) and/or to diseases associated with excessive blood brain barrier permeability, which are contemplated herein to include both neuroinflammation and/or neuroautoimmunity conditions, and especially amyotrophic lateral sclerosis, Parkinsons disease, multiple sclerosis, Alzheimer’s, or peripheral neuropathy, and major depression.