http://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/8338

"Values >0.02 nmol/L are consistent with a diagnosis of acquired myasthenia gravis (MG), provided that clinical/electrophysiological criteria support that diagnosis."

I questioned my neuro once about levels because I thought if I felt better the test should be redone to check for improvement. His comment was...If you have it you have it...no need to recheck the antibody test.
I would research what you learned.

Mayo Clinic test result info at

http://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/8338

Some of what is posted there

Values >0.02 nmol/L are consistent with a diagnosis of acquired myasthenia gravis (MG), provided that clinical/electrophysiological criteria support that diagnosis.

The assay for muscle acetylcholine receptor (AChR) binding antibodies is positive in approximately 90% of nonimmunosuppressed patients with generalized MG.

The frequency of antibody detection is lower in MG patients with weakness clinically restricted to ocular muscles (71%), and antibody titers are generally low in ocular MG (eg, 0.03-1.0 nmol/L).

Results may be negative in the first 12 months after symptoms of MG appear or during immunosuppressant therapy.

Note: In follow up of seronegative patients with adult-aquired generalized MG, 17.4% seroconvert to positive at 12 months (ie, seronegativity rate at 12 months is 8.4%). Thirty eight percent of persistently seronegative patients have muscle-specific kinase (MuSK) antibody.

Sera of nonmyasthenic subjects bind per liter 0.02 nmol or less of muscle AChR complexed with (125)I-labeled-alpha-bungarotoxin.

In general, there is not a close correlation between antibody titer and severity of weakness, but in individual patients, clinical improvement is usually accompanied by a decrease in titer.
(you should read the rest)

It has been summed up nicely for you...You have MG

Russ is quoting the 90% that should read "90% of the people Mayo diagnoses with MG" instead of "90% of the people with acquired MG."

When an institution turns away questionable prospects or refuses to diagnose people who are seronegative for their (Mayo's) testing, the percentage positive will be higher.

Reporting statistics in this manner affects diagnosis and treatment of many people with MG, not just those seen at Mayo and the word is out--if you are seronegative, don't go to Mayo. A respected institution should recognize selection bias and word its statistics in a way that reflects reality.

That doesn't mean that the tests are not valid for those patients with autoimmune myasthenia gravis fortunate enough to have positive ones. There are other tests that are not commercially available and other known antibodies. It is tragic that treatment of a disease whose clinical diagnosis is usually so straightforward has been thwarted and delayed by negative testing. b.

This is so Frustrating! Why are the ranges so different?? Does any one know??

The lab my sample was sent to determines below 0.25nmol/L as negative/normal. I don't take any medication that might affect the reading. I'm in the UK and being told I have "Functional Disorder" and that my muscles aren't working properly but no further testing or treatment has been offered? I see my GP tomorrow so I am trying to get as much info as possible before I go!

Thanks again everyone - I have printed the Mayo Clinic Info and Medscape info.

The whole thing is very tedious and frustrating. First of all, those antibodies should not be in the human body in any concentration, so why does the test allow for it? Second of all, there is no correlation between the count and severity of illness, so how can treatment be dictated by the test? My doctor told me the numbers were only somewhat useful once a baseline has been established for the individual. Thanks, b, for chiming in.

I think I disagree with the Mayo comment: read what it says

"Note: In follow up of seronegative patients with adult-aquired generalized MG, 17.4% seroconvert to positive at 12 months (ie, seronegativity rate at 12 months is 8.4%). Thirty eight percent of persistently seronegative patients have muscle-specific kinase (MuSK) antibody. "

Obviously indicates there are seronegative patients with generalized MG included.

Well, Russ, they let us lose all our health while they pick lint out of their navels. And there is no reason for the antibodies to be there. There current tests are insufficient, and people lose their lives during the diagnostic process.

Russ,
This is my hobby horse and could be yours, too, since you are a researcher. My problem with these kind of statistics is not just with Mayo. It is just the worst example I have seen given the 90% AChR+ figure.

That figure is based on their institution only and requires that they properly diagnose everyone with MG that comes through the door--it isn't happening. They have a selection bias to begin with--as is almost always the case, especially for a referral site. The MOST they can say that in their diagnosed cases of MG, AChR antibodies are found on testing in 90%. MuSK throws in another 5% or so and there is a small percentage who convert. These are not seronegative patients and neither are the very small percentage with MG they follow with persistently negative blood tests, but calling these people seronegative is another misleading matter. (Never mind for now, most people know that.)

Handing out statistics like that give the impression to practicing neurologists that if they just play the percentages, they will pick up at least 95% of the people with "real MG" just by testing their blood. It would be bad enough even if it picked up 99% and they missed one out of a hundred. It affects almost every one of us because most of us do not get treated until the tests come back and it is especially hard on people like the 50% of the participants at the Atlanta meeting with diagnosed MG who are "seronegative."

Although they and we, too, may suffer from self selection bias, it is a rare person on this board who has been given a clinical diagnosis and treatment before testing. It is not a rare experience that given negative testing and prior treatment, that treatment has been withdrawn. Not to mention all the other testing that follows or doesn't follow.

Negative testing also affects options for treatment when insurance companies as well as neurologists believe those kind of statistics are representative of the entire population of people with autoimmune myasthenia. I think it is extremely insensitive to support such information when you have the ability to weigh the validity.

There is a lot of misinformation out there about MG and it takes more than Wikipedia and Google to sort through it. I do not want to spend my days in endless research and am no longer practicing, but I can recognize basic problems--selection bias and testing error and practitioner error and false positives and negatives are basic problems.

B, I have a question for you. My results are always in "CPM". Do you know how I would convert that to nmol/L?

Linda

About Mayo Clinic medical laboratories:
Performs nearly 20 million tests for more than 4,000 hospitals annually (obviously not just for patients coming through the door at Mayo).
Comprises more than 3,200 employeesincluding more than 160 physicians and scientists
Has 58 laboratories that perform testing with consultative support from Mayo Clinic physicians
Utilizes efficient support systems to keep costs affordable for patients, while consistently maintaining excellent quality
Serves clients in more than 130 countries

The MG diagnosis references are at
http://www.mayomedicallaboratories.com/interpretive-guide/index.html?alpha=M&unit_code=83370

Diagnosing someone to have MG who does not have any of the tests positive (i.e, antibody, emg, clear symptoms, etc) certainly runs the risk of being diagnosed with the wrong disease. I think that is worse than having no diagnosis. It is certainly hard for a patient to endure being undiagnosed, but better than misdiagnosed.

So when a patient comes in saying they have MG, and yet the tests are negative and the symptoms not a good match, do you let the patient make the determination?

I think Mestinon should always be given (in moderation of course) to the people that are suspected to ahve MG and test negative...Just to see how they react. That would eliminate many misdiagnoses or not diagnosed also.

In a perfect world that is...