PNS autoantibody represent a special group of autoantibody in the area of neurology, which are associated with paraneoplastic neurological syndromes (PNS). PNS are defined as neurological clinical syndromes that accompany malignant tumours, but are not directly caused by them or their metastases, are not of vascular or infectious origin and do not result from therapy-related side effects. They are caused by tumour-released immunological mechanisms, which take their effect distally from the primary and/or metastatic tumour site. Depending on the type of tumour, tumour cells express antigens, e.g. amphiphysin, CV2/CRMP5, PNMA2 (Ma2/Ta), Ri, Yo or Hu, which can induce the formation of specific autoantibody. These autoantibody bind to the respective antigens localised in the nervous tissue and are thus probably involved in neurological disorders. The antigen-antibody reactions not only prove the paraneoplastic aetiology to almost 100%, but they are also closely related to specific tumours which up until that time were undetected in these patients. PNS autoantibody detection is therefore very useful in the diagnosis of tumours in their early stages. 

PNS occur in approx. 15% of malignant diseases, occur most frequently in association with small-cell lung carcinoma (SCLC), breast or ovarian carcinoma. Lambert-Eaton myasthenic syndrome (LEMS), which is the most frequent PNS and can be diagnosed by determining Purkinje cell antibodies, has the highest predictive value with respect to an underlying tumour (here SCLC). In most PNS, particularly in paraneoplastic limbic encephalitis (PLE), paraneoplastic cerebellar degeneration (PCD), paraneoplastic opsoclonus myoclonus ataxia (POMA), stiff-person syndrome (stiff-man syndrome) and retinopathy (subacute amaurosis), the detection of specific antibodies has a much higher predictive value with respect to the presence of a tumour than the clinical symptoms by themselves. 
The EUROLINE Paraneoplastic Neurologic Syndromes 12 Ag is not suitable for the detection of antibodies against GAD65 in diabetes mellitus. A negative result in the EUROLINE does not exclude the presence of Anti-GAD65.
For the medical diagnosis, the clinical symptoms of the patient and, if available, further findings should always be taken into account alongside the serological result. A negative serological result does not exclude the presence of a disease because this test can determine autoantibodies of the immunoglobulin class IgG against only 12 different antigens.  Not all of the target antigens of autoantibodies associated with paraneoplastic syndromes have yet been identified, purified and sufficiently validated.