I haven't specifically billed either specialty. IMO, if you have a good grasp on billing as a whole, and you have experience in other specialties, you will be able to pick up what is needed for a specialty you haven't billed. In my experience, when I have had to start a specialty I haven't done before I was able to use my previous experience in other specialties and my ability to research what was needed to be able to learn the new specialty. I'm not advocating going out and 'winging it'. I just believe that an experienced and responsible biller can do what is needed to learn the new specialty. I am always up front with a provider when approached for a specialty I haven't billed for, but I'm confident in my ability to learn what is needed.