Abstract Details

Title Glutamic Acid Decarboxylase 65 Antibody Titer Levels Help Differentiate Stiff Person Syndrome Spectrum Disorders from Other Conditions

Topic Autoimmune Neurology

Presentation(s) P1 - Poster Session 1 (8:00 AM-9:00 AM)

Poster/Presentation
Number 14-004

Objective To characterize glutamic acid decarboxylase 65 (GAD65)-antibody (Ab) testing patterns along with associated clinical findings and differentiating properties of titer levels with a stiff person syndrome spectrum disorder (SPSD) diagnosis.

Background Anti GAD65-Ab seropositivity is commonly encountered in clinical practice. These autoantibodies can be associated with several systemic disorders as well as neurologic disorders such as SPSD. The lack of specificity of GAD65-Ab makes it a challenging biomarker for differentiating between disorders and can lead to misdiagnoses.

Design/Methods We conducted a retrospective chart review of GAD65-Ab labs completed though the Johns Hopkins laboratories (n=2894); Enzyme Linked Immunoassay method was utilized. We assessed data from all neurology clinics determining reason(s) for GAD65-Ab testing and documenting final/working diagnosis determined by treating clinician. Abnormal values were separated into quartiles to assess potential thresholds for diagnoses.

Results Neurology providers ordered 29.0% of GAD65-Ab labs (840/2894). GAD65-Ab was abnormal (titer >5.0 IU/mL) in 30.3% of all samples (877/2894) and in 44.4% of neurology ordered labs (373/840). Most common reasons for ordering GAD65-Ab were stiffness and spasms. Abnormal GAD65-Ab titers ranged from 5.1 to 6,690,000 IU/mL. Mean age (range) of patients with abnormal GAD65-Ab was 55 years (18 – 88) and 72.7% were female. All patients with abnormal GAD65-Ab in 3^rd and 4^th quartile values (mean titer; range) (176,059; 52,850 – 379,735.4 IU/mL and 1,065,179; 382,541 – 6,690,000 IU/mL, respectively) and 90% in 2^nd quartile (14,958; 338.6 – 51,517 IU/mL) were diagnosed with SPSD. In contrast, 44% in the first quartile (115.9; 5.1 – 333 IU/mL) were determined to have a diagnosis other than SPSD. Future analyses will include data from non-neurology clinics.

Conclusions GAD65-Ab testing is often requested by neurology and non-neurology providers for various reasons. GAD65-Ab titers vary widely depending on the associated condition. However, high titers appear specific for an SPSD diagnosis in the appropriate clinical setting.

Authors/Disclosures
Aisha Elfasi, MD PRESENTER	Dr. Elfasi has nothing to disclose.
Brendan Lindgren, DO	Dr. Lindgren has nothing to disclose.
Patrizio Caturegli (Johns Hopkins University)	No disclosure on file
Herbert Chen	Herbert Chen has nothing to disclose.
Ashley Miles (The Johns Hopkins Hospital)	No disclosure on file
Scott D. Newsome, DO, FAAN (Johns Hopkins Hospital)	Dr. Newsome has received personal compensation in the range of $10,000-$49,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Genentech. Dr. Newsome has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Novartis. Dr. Newsome has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for TG Therapeutics. The institution of Dr. Newsome has received research support from Biogen. The institution of Dr. Newsome has received research support from Genentech/Roche. The institution of Dr. Newsome has received research support from Department of Defense. The institution of Dr. Newsome has received research support from Patient Centered Outcomes Research Institute. The institution of Dr. Newsome has received research support from National MS Society. The institution of Dr. Newsome has received research support from Lundbeck. The institution of Dr. Newsome has received research support from Sanofi. The institution of Dr. Newsome has received research support from Kyverna Therapeutics. Dr. Newsome has received personal compensation in the range of $10,000-$49,999 for serving as a Lead PI for Clinical Trial with Roche.

��ɫ��

��ɫ��