Abstract
BACKGROUND: Encephalitis is a devastating neurological disorder resulting in high mortality and morbidity in seemingly healthy patients. Historically most cases of encephalitis have been attributed to infection. However, over the last decade encephalitis due to autoimmune etiology has come to the forefront with the aid of newly discovered antibodies that correlate with specific encephalitis syndromes. We became concerned of overreliance on antibody panels in determining etiology of illness in patients presenting with unusual neurologic conditions. RESULTS: In this retrospective clinical study we reviewed 73 patient cases for whom 92 autoimmune antibody panels were ordered from Mayo Clinic Laboratories in Rochester, Minnesota over September 1 - November 30, 2016. We found 11 cases of positive GAD65 antibodies (0.03-0.20 nmol/L, ref < 0.02 nmol/L), 2 cases of ganglionic acetylcholine receptor antibodies (gAchR-Ab), 1 case of positive NMDA receptor antibodies, and 1 case of both voltage gated potassium and calcium channel antibodies. Clinical syndrome of autoimmune epilepsy and encephalopathy was diagnosed in patient with positive NMDAR-Ab. Patients found to have the other positive antibodies did not have clinical syndromes previously reported to be associated with the specific antibody. One patient with Hashimoto’s encephalitis was found to have positive gAchR-Ab. Five other patients were diagnosed with nonspecific autoimmune encephalitis; 1 positive for gAchR-Ab, 1 for GAD65-Ab, 3 with negative studies. DISCUSSION: We found very low frequency of appropriate antibody panel ordering behavior fitting a specific clinical syndrome. High number of false positive and incidental results may misdirect patient care and therapeutic intervention. Our results emphasize that the presence of low titer antibodies without a specific clinical syndrome may not be of utility, and that the absence of antibodies where a certain clinical syndrome is suspected should not exclude the diagnosis. We plan to continue this study, and educate our physicians regarding this important matter.