The difference is about 9+ years of medical schooling.
Also, my protocol says ANYONE complaining of SOB or difficulty breathing gets atleast some 02.
In addition, Your confusing a field impression with an actual clinical diagnosis.
I can think someone has hyperkalemia due to other symptoms and field tests (vitals, EKG, etc),but until I have labs, all it is is a field impression of what I THINK is probably wrong. I do not have a ct scan. I can't diagnose a stroke. I can say someone failed the Cincinnati stroke scale, is hypertensive, and I am fairly certain they are having a stroke, but without a head scan I can not diagnose it.
So no. We do not diagnose. Our treatments are based off of a field impression of what's probably wrong, based on signs and symptoms. It is not definitive.