ME/CFS is the name used in the Canadian Consensus Criteria, so it does have a formal usage.
The name was chosen in 2003 to reflect the placement of both ME and CFS in ICD-10 under the chapter on neurology at G93.3. Many patient advocates believe the Canadian Consensus Critera represents the best current definition in use.
In the US, myalgic encephalomyelitis was never used. When British researchers began using M.E., the US instead used Epidemic Neuromyesthenia. However, Alex Shelekov, the national expert on epidemic neuromyesthenia, sided with those at the 1988 Holmes meeting who said the cluster outbreaks were M.E. That was not even included in a footnote, but in a companion article the same year, the late Stephen Straus wrote that CFS was also once known as epidemic neuromyesthenia and, without using the term M.E., nevertheless referenced the two McAvedy and Beard articles suggesting M.E. was really mass hysteria, using them to lend authority to his assertion that researchers knew CFS patients actually had mental problems.
To introduce the term ME to the US medical establishment, many advocates - dating back to the late 1990s - had suggested the use of ME/CFS and ultimately dropping the CFS part. I suggested it myself when presenting at a special name change session on the AACFS program in 1998, but I was not the only one.
In 1998 CDC removed 323.9, the designation for M.E., from ICD-9-CM. Doctors in the U.S. have to use those codes for insurance reimbursement, so that was tantamount to rendering the disease nonexistent. As it was, most doctors in the US refused to give that diagnosis when asked. Now it required a second diagnosis for reimbursement.
After patients began clamoring for the adoption of the Canadian Consensus Criteria that linked M.E. and CFS, CDC added a statement to ONE of their websites to the effect that the two were not the same thing. I thought at the time it was not a recognition of M.E. (because you will find nothing on M.E. anywhere else at CDC), but an effort to negate the movement to adopt the Canadian Criteria.
Personally, I was surprised and delighted that the CFSAC recommended the use of the term ME/CFS because it would place CFS in G93.3 in ICD-10-CM, which is still not scheduled for adoption until at least 2013. The rest of the world is looking on to ICD-11, but the US is still on ICD-9.
The CFSAC is an advisory committee to the Secretary of Health and Human Services, who oversees both CDC and NIH. It is well within their purview to recommend the use of ME/CFS, and well within the purview of NIH to follow that recommendation in an exploratory workshop on the state of the knowledge, for now.
Finally, while I fully appreciate why patients in nations that have a history of M.E. would like to get rid of CFS entirely and not see it paired with M.E., please understand that doing so in the US means that CFS, the only name used in the vast majority of the medical establishment in the US (who never heard of M.E.), will be placed in R53 under "vague signs and symptoms" - not G93.3, in neurology, in ICD-10-CM.