Buddy, the single fiber EMG is the most sensitive of tests. It takes considerable skill, so the doctor who does it would be a step above a doctor who does standard EMGs. Definitely go for the single fiber. The other EMG you have had an appointment for, would be redundant after the single fiber.
Single fiber will show if there is MG or
ALS, but cannot differentiate between the two, so that is why your other test results ( NCV, for example) are important, and your clinical exam findings will also have added weight to them if any abnormalities do show with the single fiber test.
If your single fiber is normal, then you absolutely need to cross fears of
ALS off of your list. In a clinical trial of (?? maybe 45??) confirmed
ALS patients, along with a control group, 100% of those with
ALS had abnormal single fiber EMGs.... I believe that this test detects MG in about 90% of people who have it.
good luck to you