What are the current guidelines for Jehovah's Witnesses regarding blood use in medical treatment?

There have been a lot of new methodologies developed in medicine that isolates specific fractions of blood for use in specific needs of individuals. Whole blood is rarely transfused anymore. My understanding is that a wide variety of fractions of blood are now being accepted as medical therapy by Jehovah's Witnesses. What exactly is the official position of JWs now as regards use of blood and blood products for patients?