Since medical sciences advances rapidly, guidelines are often dated even before they are published. Some of the resulting gap can be filled by consensus statements, in many cases endorsed by various scientific societes.
I was involved in many consensus statements as medical writer. The process starts with a meeting I take part in, then I write a draft that goes to the chair persons first and then to all participants who are invited to give their feedback. The result is a consensual text addressing a current medical subject (you can find some examples of such text here).
For the organisation of such meetings I have successfully been relying on the company „Medical Dialogue“ (Owner: Karl Buresch).