Having low or borderline AChR antibody levels can make getting a clear MG diagnosis tricky. A normal AChR antibody result doesn't automatically rule out MG — about 1 in 5 people with MG don't have detectable AChR antibodies at all.
If AChR levels are borderline or negative, doctors will typically look further. Here's what Show Full Answer
Having low or borderline AChR antibody levels can make getting a clear MG diagnosis tricky. A normal AChR antibody result doesn't automatically rule out MG — about 1 in 5 people with MG don't have detectable AChR antibodies at all.
If AChR levels are borderline or negative, doctors will typically look further. Here's what that process usually looks like:
- MuSK antibody test — Up to 40% of people who test negative for AChR antibodies test positive for MuSK antibodies instead
- LRP4 antibody test — If both AChR and MuSK tests are negative, doctors may test for LRP4 antibodies, another protein involved in nerve-muscle communication
- Seronegative MG diagnosis — If all antibody tests come back negative but symptoms match MG, a seronegative MG diagnosis may be given Around 6–12% of people with MG have neither AChR nor MuSK antibodies, making seronegative MG the rarest type. It tends to show up more in younger people and females, and symptoms often focus on the eyes and face (like drooping eyelids, double vision, or trouble swallowing) rather than generalized muscle weakness.
It's worth having an open conversation with a neurologist about further testing if results feel inconclusive — a diagnosis can sometimes take time, but there are multiple paths to get there.
May 24
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