Clinical and Autoimmune Profiles of Omani Patients with True Versus False Positive Autoimmune Encephalitis Antibodies...

This study aimed to explore the clinical profiles of Omani patients with true-positive autoimmune encephalitis (AE) autoantibodies and compare them with those having false-positive autoantibodies. The incidence of AE is rising due to growing awareness and the detection of new autoantibodies. Coinciding with this rise are false positive autoantibodies without clinical correlates.

The medical records of all patients who tested positive for AE antibodies in Sultan Qaboos University Hospital, Muscat, Oman, from May 2016 to December 2022 were reviewed. Cases were verified by three neurologists based on the existing criteria for AE.

The participants comprised 67 patients, 19 (28%) of whom met the criteria for AE. True-positive AE patients had a mean age of 35.3 ± 4.7 years (P = 0.010) and were more likely to present with subacute memory disturbances (6/19; 32%; P = 0.030), seizures (12; 63%; P = 0.028), abnormal electroencephalogram findings (10; 65%; P = 0.040) and abnormal signals in the limbic region on magnetic resonance imaging (5; 26%; P = 0.010). Subacute memory disturbance was a significant predictor for true positivity (OR = 17.807, 95% CI = 1.608-197.202; P = 0.019). Anti-N-methyl-daspartate receptor (NMDAR) encephalitis was the most frequent type of AE (8; 42.1%), followed by anti-glutamic acid decarboxylase 65 (GAD65) (4; 21.1%).

Of the 67 cases with positive AE autoantibody panel, 48 (72%) were false positive. Further, the presence of subacute memory impairment was a predictor of AE, and anti-NMDAR encephalitis was the most frequent AE encountered in the cohort.