A healthcare professional conducts a physical examination to collect basic information about the patient's overall health and assess potential symptoms related to the disease.^4,6 This may include an evaluation of potential weakness in affected muscle groups, such as those of the eyes, face, limbs or those required for breathing, talking, chewing or swallowing.^4,6 For example:

Some possibilities of what to expect during a physical examination:

• Eye movement evaluation or ice applied to the eyelid^4,6
• Swallowing, speaking and/or breathing assessments^4,6
• Breathing into a handheld device⁴
• Arm and/or leg movement evaluation^4,6

Blood testing is the primary method to confirm a diagnosis of MG by determining the presence of specific proteins, known as autoantibodiesAntibodies produced by the immune system that mistakenly target and attack the body’s own tissues or cells ,^8,9 that are involved in the development of the disease.¹⁰ These autoantibodies are produced by the body’s own defence mechanism, the immune system, and mistakenly attack and disrupt the communication between nerves and muscles.^10,11

There are three main types of autoantibodies that are assessed through blood testing in MG⁴:

• Autoantibodies against the acetylcholine receptor (AChR), which are found in about 80–85% of patients with MG^9,10,12
• Autoantibodies against muscle-specific kinase (MuSK), which are present in about 6–8% of patients with MG^8,9
• Autoantibodies against low-density lipoprotein receptor-related protein 4 (LRP4), which may be detectable in about 2% of patients with MG^8,9

Blood testing is also useful for the evaluation of various other parameters relevant to patients with suspected MG.⁴

Some possibilities of what to expect during blood testing:  

• Blood draw from arm

Nerves normally control muscles by sending electrical signals to the muscles.¹¹ In individuals with MG, the electrical signalling between nerves and muscles is interrupted,¹¹ and this can be detected with so-called electrophysiological tests.¹³ Such tests are particularly important in patients for whom blood tests do not detect autoantibodies Antibodies produced by the immune system that mistakenly target and attack the body’s own tissues or cells related to MG.^1,13 The main electrophysiological tests in MG are^1,13:

• Repetitive nerve stimulation (RNS)

  During RNS, electrodes (small metallic pieces) are placed on the patient’s skin to stimulate the nerves with small pulses of electricity and assess the ability of nerves to send electrical signals to the muscles over repeated rounds of stimulation.^11,14
• Single-fibre electromyography (SF-EMG)

  During SF-EMG, a small needle electrode is inserted into the patient’s muscles to detect potential abnormalities in the electrical signalling between the nerves and the muscles.^1,11

Some possibilities of what to expect during electrophysiological testing:

• Repetitive nerve stimulation (RNS) – Electrodes (small metallic pieces) placed on the skin¹⁴
• Single-fibre electromyography (SF-EMG) – Needle electrode inserted into muscle¹

During pharmacologic tests for MG diagnosis, the patient receives an injection of a drug – an acetylcholinesterase inhibitor – that increases temporarily the amount of a chemical called acetylcholine in the body.^5,8 Increased acetylcholine levels in a patient with MG can improve the communication between nerves and muscles, thereby improving muscle strength.^3,5,8 Therefore, if an improvement in muscle strength is observed after receiving the drug, this would be considered an indication of MG.^3,8 Such tests may be performed in some patients but may not be suitable in others.^3–5,8 The most known pharmacologic test of this type is the so-called edrophonium test (also called Tensilon test), during which the patient receives an intravenous injection of an acetylcholinesterase inhibitor called edrophonium chloride.^5,8

What to expect during pharmacologic testing:

• Injection of a drug^5,8

Patients with suspected MG may also undergo imaging tests.^4,7 These tests are performed to identify or exclude the presence of tumours (also known as thymoma) in an organ called the thymus that is located in the chest,^4,7 as up to 15% of patients with MG may have thymomas.⁸ Images of the chest can be acquired using thoracic computed tomography (CT) or magnetic resonance imaging (MRI).^4,7 Both techniques involve the patient lying on a flat bed that passes through a scanner and may require administration of a dye – otherwise known as a contrast agent – to the patient beforehand to obtain clearer imaging.^15,16 An MRI scanner is shaped as a cylinder that is open at both ends,¹⁵ whereas a CT scanner is ring-shaped and rotates around a small section of the body while the patient is passing through.¹⁶

Some possibilities of what to expect during imaging:

• Possible administration of a dye (for example, in the form of an injection)^15,16
• Lying on a flat bed that passes through a CT or a MRI scanner^15,16