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Abstract Details

Testing for N-type Voltage Gated Calcium Channel Antibody has limited utility in evaluating patients with suspected Lambert-Eaton Myasthenic Syndrome
Autoimmune Neurology
P1 - Poster Session 1 (9:00 AM-5:00 PM)
065
To determine if testing for N-type voltage-gated calcium channel antibody improves diagnostic performance of serological testing for Lambert-Eaton Myasthenic Syndrome.
Patients with suspected autoimmune neuromuscular junction transmission disorders are commonly tested for both P/Q-type (VGCC-P/Q) and N-type (VGCC-N) voltage-gated calcium channel antibodies to aid the diagnosis of Lambert-Eaton Myasthenic Syndrome (LEMS).
This retrospective cross-sectional study included 93 patients diagnosed at Mayo Clinic with LEMS based on electrodiagnostic findings, clinical presentation and positive serology for VGCC-P/Q and/or VGCC-N.
Forty-five patients (48.4%) were female, of median age 61 years (range 11- 99). Twenty-five (26.9%) were positive for both VGCC antibody types (reference interval <0.04 nmol/L [VGCC-N] and <0.03 nmol/L [VGCC-P/Q]); 67 (72.0%) were positive for VGCC-P/Q only and one (1.1%) was positive for VGCC-N only. The single VGCC-N positive only result [VGCC-N= 0.10 nmol/L; VGCC-PQ= 0.02 nmol/L] was from a patient with classic LEMS presentation and no evidence of malignancy by Chest CT. The prevalence of VGCC-N only positivity was lower than in the healthy population or other disease control populations. VGCC-P/Q antibody titers were higher in patients who had detectable co-existing VGCC-N antibody (median titer 1.58 versus 0.39 nmol/L, P=0.02) and there was a positive correlation (r=0.762, P<0.001) between VGCC-N and VGCC-P/Q titers in double positive cases. Dual positivity did not significantly increase the likelihood of an underlying cancer (40.9% versus 30.1%, P=0.33).

Testing for VGCC-P/Q antibodies alone is sufficient in the serological evaluation of suspected LEMS cases. Inclusion of VGCC-N antibody testing does not improve diagnostic performance. A positive VGCC-N antibody did not significantly increase the risk of paraneoplastic LEMS.
Authors/Disclosures
Masoud Majed, MD
PRESENTER 		Dr. Majed has nothing to disclose.
Anastasia Zekeridou, MD, PhD, FAAN (Neuroimmunology Laboratory, Mayo Clinic) The institution of Dr. Zekeridou has received research support from Roche/Genentech. Dr. Zekeridou has received intellectual property interests from a discovery or technology relating to health care. Dr. Zekeridou has received intellectual property interests from a discovery or technology relating to health care. Dr. Zekeridou has received intellectual property interests from a discovery or technology relating to health care. Dr. Zekeridou has received intellectual property interests from a discovery or technology relating to health care.
Vanda Lennon, MD, PhD (Mayo Clinic) The institution of Dr. Lennon has received research support from NIH. Dr. Lennon has received intellectual property interests from a discovery or technology relating to health care.
Sean J. Pittock, MD, FAAN (Mayo Clinic Dept of Neurology) Dr. Pittock has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Arialys. The institution of Dr. Pittock has received personal compensation in the range of $5,000-$9,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Alexion. The institution of Dr. Pittock has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for UCB. The institution of Dr. Pittock has received personal compensation in the range of $5,000-$9,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Roche/Genentech. The institution of Dr. Pittock has received personal compensation in the range of $10,000-$49,999 for serving on a Speakers Bureau for Alexion/AstraZeneka. The institution of Dr. Pittock has received research support from NIH. Dr. Pittock has received intellectual property interests from a discovery or technology relating to health care. Dr. Pittock has received intellectual property interests from a discovery or technology relating to health care. Dr. Pittock has received publishing royalties from a publication relating to health care.
Andrew McKeon, MD (Mayo Clinic) The institution of Dr. McKeon has received research support from National Institutes of Health. Dr. McKeon has received intellectual property interests from a discovery or technology relating to health care. Dr. McKeon has received intellectual property interests from a discovery or technology relating to health care. Dr. McKeon has received publishing royalties from a publication relating to health care.
Christopher J. Klein, MD, FAAN (Mayo Clinic) Dr. Klein has received personal compensation in the range of $500-$4,999 for serving as a Consultant for NMD Pharma.
Divyanshu Dubey, MD, FAAN (Mayo Clinic) The institution of Dr. Dubey has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Argenx. The institution of Dr. Dubey has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Arialys. The institution of Dr. Dubey has received personal compensation in the range of $500-$4,999 for serving as a Consultant for UCB . Dr. Dubey has received research support from Department of Defense . Dr. Dubey has received research support from Department of Defense . Dr. Dubey has received research support from UCB. Dr. Dubey has received research support from David J. Tomassoni ALS Research Grant Program . Dr. Dubey has received intellectual property interests from a discovery or technology relating to health care. Dr. Dubey has received intellectual property interests from a discovery or technology relating to health care. Dr. Dubey has received intellectual property interests from a discovery or technology relating to health care. Dr. Dubey has received intellectual property interests from a discovery or technology relating to health care.
John R. Mills, MD, PhD (Mayo Clinic) The institution of Dr. Mills has received research support from Werfen Diagnostics. Dr. Mills has received intellectual property interests from a discovery or technology relating to health care.