How Accurate Is The Blood Test For Myasthenia Gravis?

Myasthenia gravis is a disorder in which the voluntary muscles in your body typically get weakened and become quickly exhausted or fatigued. This happens when there is a lack of proper communication between muscles and nerves. Myasthenia gravis cannot be cured.

How Accurate Is The Blood Test For Myasthenia Gravis?

How Accurate Is The Blood Test For Myasthenia Gravis?

Blood tests in myasthenia gravis can be useful in the initial stages of the condition, to establish a confirmed diagnosis. However, the blood tests cannot determine the stage or severity of the disorder. Blood tests may also be able to diagnose a thymoma- a tumor of the thymus gland.

Anti-Acetylcholine Receptor Antibody Test-

This test is quite a reliable one in diagnosing myasthenia gravis. However, if only ocular myasthenia gravis is present, it may not show in the results and hence, there is a chance of getting a false negative test. High levels of this antibody in the blood may indicate myasthenia gravis, which may not be detected in case of only ocular myasthenia gravis. When myasthenia gravis affects other parts of the body, the antibodies may increase and may be detectable in the blood. (1)

Other Diagnostic Methods For Myasthenia Gravis

The doctor will ask you for your complete medical history. He will ask you about onset of symptoms and the duration for which you have had those symptoms. He will also conduct a thorough physical examination. He may also perform or recommend several tests, which may include but are not limited to-

Neurological Tests-

  • Your doctor will check for your reflex actions, strength and tone of your muscles, your tactile and sight senses, your balance and coordination etc.
  • If there is a muscle weakness of the voluntary muscles that peculiarly gets better after rest, it may be indicative of myasthenia gravis (2)

To further confirm this, other tests may be carried out, which may be including but not limited to-

  • Edrophonium Test– If a chemical called edrophonium chloride is injected in your body and your muscles show improved muscle strength, it may be suggestive of myasthenia gravis. This improvement in muscle strength is, however, temporary.
  • Ice Pack Test– This test may be conducted in case of droopy eyelids. Your doctor may place a bag of ice on your droopy eyelid for about two minutes. If your droopy eyelids get better after two minutes of ice therapy, it may be suggestive of myasthenia gravis. This test may be used in place of edrophonium test.
  • Nerve Stimulation– In this test, electrodes are attached to the skin on the muscle that is to be tested. Small electricity signals are sent through these electrodes and the ability of the nerve to send signals to the muscles is tested. It is observed whether this ability gets weakened with fatigue.

EMG Or Electromyography-

This test checks the electrical activity between the brain and muscle

Imaging Tests-

A CT scan or an MRI may be recommended by doctors to check for any abnormality like tumors in the thymus

PFT Or Pulmonary Function Test-

This test may be done to check if myasthenia gravis is affecting your respiratory system or breathing muscles. (2)

Treatment Of Myasthenia Gravis

Most cases of myasthenia gravis do not need any treatment. However, those that do have several options at their disposal. The doctors will choose a suitable line of treatment for you according to your age, area which is affected by the condition, duration and onset of the condition, severity of your condition and other underlying medical conditions present if any.

The treatment may be in the form of one or many of the following-

Medications Like-

  • Cholinesterase inhibitors
  • Corticosteroids
  • Immunosuppressants

Intravenous Therapies Like-

  • Plasmapheresis
  • Intravenous immunoglobulin
  • Monoclonal antibody
  • Surgery
  • Thymectomy (2)

Blood tests for myasthenia gravis are usually accurate when it is present in major part of the body. It has not proven to be accurate in instances of ocular myasthenia gravis.

References-

  1. https://emedicine.medscape.com/article/1171206-workup
  2. https://www.mayoclinic.org/diseases-conditions/myasthenia-gravis/diagnosis-treatment/drc-20352040

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