Ganglionic Antibody Level as a Predictor of Severity of Autonomic Failure.

OBJECTIVE:To assess antibody level as a test of autonomic failure (AF) associated with ganglionic nicotinic acetylcholine receptor antibody (AChR-Ab) autoimmunity. PATIENTS AND METHODS:We searched the Mayo Clinic laboratory database of 926 ganglionic AChR-Ab-seropositive patients seen at our institution between October 1, 1997, and April 1, 2015, for initial level of 0.05 nmol/L or higher and contemporaneous autonomic reflex screen (standardized evaluation of adrenergic, cardiovagal, and sudomotor functions) from which Composite Autonomic Scoring Scale (CASS) scores could be calculated. RESULTS:Of 289 patients who met inclusion criteria, 163 (56.4%) were women, median age was 54 years (range, 10-87 years), median antibody level was 0.11 nmol/L (range, 0.05-22.10 nmol/L), and median CASS total score was 2.0 (range, 0-10). Using receiver operating characteristic curve analysis, a level above 0.40 nmol/L predicted severe AF (CASS score, ≥7) with 92% specificity and 56% sensitivity. For at least moderate AF (CASS score ≥4 and anhidrosis ≥25%), a level of at least 0.20 nmol/L had 80% specificity and 59% sensitivity. Levels below 0.20 nmol/L were not predictive of the presence or absence of AF. For predicting orthostatic hypotension, ganglionic AChR-Ab level had excellent specificity above 0.4 nmol/L but lacked sensitivity. Autoantibodies to additional targets were present in 61 patients (21.1%). CONCLUSION:Ganglionic AChR-Ab level of at least 0.40 nmol/L is a moderately sensitive and highly specific marker for severe AF, as is a level of at least 0.20 nmol/L for moderate AF if CASS score is coupled with anhidrosis of 25% or more, among patients with suspected ganglionic AChR-Ab autoimmune autonomic ganglionopathy. Antibody levels of less than 0.20 nmol/L have little clinical importance in the absence of clinical AF.