Hello and thanks for the question on the forum. Diagnosing ALS takes effort and has steps involved. There are many things to consider. It normally starts with a physical exam, blood test and then scans. An MRI, for example, is done to rule out other things even though it doesn't specifically diagnose ALS. The EMG or electromyography is very helpful in diagnosing ALS, yes. This can show abnormal results if you have ALS, but your doctor could also decide from the results that you have damage to your nerves or a muscle disease that’s not ALS. Another important factor is progression. Proof that it has worsened over time is important. So, an early test may show something or not but if you repeat the test, if things have progressed, this helps doctors diagnose ALS and see where someone is at with disease progression. https://www.webmd.com/brain/how-doctors-diagnose-als#1 Overall, EMG is the gold standard for diagnosis of ALS and important test to have for confirmation of the disease.