Myasthenia gravis &
An algorithmic approach to expedite diagnosis and treatment
Diagnosis of myasthenia gravis and Lambert-Eaton syndrome relies on characteristic clinical and electrophysiological findings; however, autoantibody profiles aid in screening for and confirming disease presence. Our diagnostic testing algorithm consists of upfront and confirmatory antibody testing, followed by automatic second-line testing.
Diagnose confidently with enhanced accuracy
First-line testing examines levels of acetylcholine receptor binding antibodies (AChR-Bi). If positive, confirmatory testing measures levels of acetylcholine receptor modulating antibodies (AChR-Mo). Using AChR-Mo to confirm AChR-Bi-positive tests enables optimized testing sensitivity and specificity by reducing false positives. In cases where AChR-Bi antibodies are not identified, testing automatically reflexes to muscle-specific kinase (MuSK) antibody testing.
Innovation enables superior methodology
The use of unique human muscle reagent (HMR) — which uses live cells to mimic the neuromuscular junction where antibody interaction occurs in humans — in AChR-Bi testing offers the highest level of testing sensitivity by providing the lowest cut-off values of receptor binding antibodies.
Incorporating first-line, confirmatory, and second-line testing:
Enables 95% specificity, 90% sensitivity, and 45% fewer false positives
Minimizes avoidable CT scans
Reduces unnecessary thymectomy and immunotherapy
Characteristic findings are weakness and fatiguability improved by rest or anticholinesterase medication. Electromyography (EMG) demonstrates decrement in muscle action potential during repetitive motor nerve stimulation. Chest CT may reveal thymic enlargement, thymoma, or thymic carcinoma.
Other neoplastic accompaniments include gynecological cancers, prostate cancer, breast cancer, and lung cancer.
Characteristic clinical findings include proximal weakness, sometimes including craniofacial involvement, which can be improved by brief exercise. Limited dysautonomia is dysfunction. EMG findings demonstrate baseline motor nerve conduction amplitude (CMAP) reduction and facilitation of CMAP following brief exercise or high-frequency nerve stimulation.
Neoplastic accompaniments include small-cell lung carcinoma in about 90% of paraneoplastic cases.
A Test in Focus
Mayo Clinic neuroimmunologist Christopher Klein, M.D., discusses how Mayo Clinic's updated, streamlined approach to confirmatory testing for the neuroimmunological disorders myasthenia gravis and Lambert-Eaton syndrome improves diagnostic accuracy.
Mayo Clinic researchers demonstrate how testing accuracy is improved through streamlined, confirmatory testing.