I understand that when coding for E/M, a new patient requires the three key components of history, exam, and medical decision making.

Where I get confused is when you have a new patient and the history is problem focused, the exam is detailed the the medical decision making is of high complexity. How do you know which is the correct code? What if you have two of the three match up, for example problem focused history and exam but mdm is of high complexity? Do you go with the code that matches the highest number of components? is there is a formula or key to choose the correct code? Any and all advice would be greatly appreciated.

Thanks