Can a health insurance company deny emergency medical coverage based on the final diagnosis?

I went to the emergency room for symptoms suggesting a life-threatening illness. It turned out I did not have a life-threatening illness and the ER doctor diagnosed something much less severe. However, now my health insurance company is refusing to pay for the emergency room fee based on that diagnosis. This seems unethical to me. My symptoms indicated an emergency, so I went to the hospital. Just because it turned out I didn't actually have a condition requiring emergency medical attention, doesn't mean my health insurance company has the right to deny me coverage.
--------------------
Have an appeal sent with a copy of the ER report. (Either the hospital can submit it as a provider appeal, or you can send it in.) Insurance companies use something called "prudent layperson" criteria for ER visits. What that means is...if the average person on the street would have felt the situation was a true medical emergency, then the insurance company will consider it a medical emergency. When they review the ER report, they'll see documentation of the symptoms you presented with, what comments/concerns you expressed to the medical staff, etc. If the medical records indicate you were in distress and that your symptoms could have been a true emergency, you'll likely win the appeal.
Source