Most MG patients in US start therapy without lab confirmation of disease

Less than half of Americans newly diagnosed with myasthenia gravis (MG) are receiving the recommended blood tests to confirm their condition, even though these results are vital for choosing the appropriate treatment.

According to new research using real-world U.S. insurance data, many patients are starting MG-specific therapies, including steroids, without official laboratory confirmation of the self-reactive antibodies that drive the disease.

The study found that patients were more than twice as likely to undergo appropriate antibody testing when their diagnosis was provided by a neurologist rather than by a primary care provider or an emergency room physician. This highlights a significant gap in care, as these blood tests are considered the “gold standard” for identifying the specific proteins being attacked by the immune system.

“The documented variation in practice suggests an opportunity to further develop and evaluate guidelines for the use of serological [blood] testing, neurophysiology examinations, the role of the neurologist in diagnosis and management of MG, the implications of social [factors], and the utility of repeat diagnostic testing in the management of MG,” scientists wrote.

The findings were reported in the study “Serological testing patterns among individuals newly diagnosed with myasthenia gravis,” published in the Journal of the Neurological Sciences.

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The role of autoantibodies in MG

MG is an autoimmune disease in which the body produces self-reactive antibodies, also known as autoantibodies, that attack proteins at the neuromuscular junction — the site where nerves communicate with muscles to trigger voluntary movement.

Targeted proteins within the neuromuscular junction include acetylcholine receptors (AChRs), muscle-specific kinase (MuSK), and low-density lipoprotein receptor-related protein 4 (LRP4). Such autoantibody attacks disrupt nerve-to-muscle communication, leading to symptoms such as muscle weakness and fatigue.

“While the diagnosis of MG can be made clinically, serologic testing for MG-specific antibodies can confirm the diagnosis and is recommended to help guide therapy,” the researchers wrote.

However, real-world data on how often these tests are actually used in MG diagnosis is limited.

To better understand this, a team of scientists in the U.S. retrospectively analyzed data from the HealthVerity U.S. pharmacy insurance claims database and nationally representative diagnostic laboratories.

They identified 5,788 newly diagnosed MG patients from January 2018 to June 2022. Participants had a mean age of 57.8 years, and 57.8% were women. The largest proportion was commercially insured (47%), followed by Medicare (26.4%) and Medicaid (25.9%).

Patients most often received an initial MG diagnosis at an outpatient visit (68.9%), and neurologists were the most common diagnosing specialists (22.6%), followed by primary care providers (16.4%) and ophthalmologists (6.2%). Nerve function testing via electromyography, the most sensitive MG diagnostic test, was rare (12.2%).

Less than half of participants (44.7%) underwent any MG-related antibody testing: 25.7% before diagnosis and 20.9% in the year after diagnosis. Those diagnosed by neurologists were nearly twice as likely to be tested as those diagnosed by non-neurologists (54.8% vs. 33%).

Statistical analyses adjusted for potential influencing factors showed that several factors were significantly associated with a lower chance of undergoing antibody testing. These included having commercial insurance (by 18%) or Medicaid (by 32%) rather than Medicare, having a higher number of simultaneous medical conditions (by 3%), living in a rural area (by 38%), and being first diagnosed in the emergency department (by 29%) or hospital (by 41%) rather than an outpatient clinic.

In contrast, receiving a diagnosis from a neurologist was significantly associated with a twofold increased likelihood of undergoing antibody testing. Other factors linked to a higher chance of testing were undergoing electromyography (by 29%), being Hispanic rather than white (by 30%), and having MG symptoms such as double vision (by 69%), drooping eyelids (by 57%), or slurred speech (by 32%).

Treatment begins despite testing gaps

Among tested patients, more than half (56.3%) tested negative for MG-related autoantibodies, 42.4% tested positive for those targeting AChR, 1.1% for anti-MuSK antibodies, and 0.2% for anti-LRP4 antibodies.

Patients diagnosed by neurologists were significantly more likely to have a positive result than those diagnosed by non-neurologists (50.6% vs. 30.3%). Of those who tested negative, slightly more than half (56.6%) were tested solely for anti-AChR antibodies, while about one-third (33.7%) underwent testing for both anti-AChR and anti-MuSK antibodies.

Despite gaps in antibody testing, most newly diagnosed patients (69.5%) started at least one MG-specific treatment within a year. The most common therapies were corticosteroids (71.7%) and acetylcholinesterase inhibitors (69.4%) — a therapy class that includes pyridostigmine (sold as Mestinon in the U.S.).

Patients who tested positive for anti-AChR antibodies were more likely to undergo treatment than those who tested negative (83.1% vs. 72.5%).

Even among the more than 3,200 patients with no blood test results, the majority (63.4%) still received MG treatment, most often corticosteroids (73.8%) and acetylcholinesterase inhibitors (62.3%).

“Many individuals with MG receive a diagnosis without the benefit confirmatory diagnostic serologic or electrophysiology examinations,” the researchers concluded. “Optimizing the use of serological testing may be an essential step to support early diagnosis and appropriate treatment selection which will lead to improved patient outcomes.”