I am always amazed and sad that any physician would base a diagnosis completely on a laboratory test. As medical students are being taught to use computers rather than their brains or commonsense, this seems to be the new way that medicine in many offices and clinics is being practiced. A patient or parent might ask why is this a problem? The answer is that there are several reasons that laboratory or genetic tests can be erroneous; blood samples can be mixed or lab technicians can get sloppy and make mistakes or not have adequate training to do the tests.
Some laboratories are very reliable while others are known to make frequent errors. Now that many new genes are being discovered, some physicians simply order blood work, send it to a lab for genetic testing and then when the results come in send the patient or parents to a genetic counselor. Some genetic counselors have Ph.Ds, while others have much less training. I would assume all physicians would want to sit down with their patient or parents and go over the tests results themselves. However, if the physician does not have adequate training or experience with a particular disorder this is an easy way to get out of answering questions.
The most important thing in diagnosing a patient with muscle weakness is still a complete physical examination and a family history with questions about any anesthetic problems. Then the blood test CPK should be ordered on the patient and often the mother. The next extremely important step is to obtain a muscle biopsy. A neuromuscular specialist will want to look at the biopsy and not leave the diagnosis to a pathologist who may not have had training in reading muscle biopsies. If there is a question, a second opinion should always be obtained.