In the UK today, I assume the NHS largely uses the
NICE guidelines to diagnose the disease they call 'CFS/ME'. In the past, when the preeminent British ME clinicians (Ramsay, Dowsett, Richardson) were still alive and practicing medicine, they used their own various case definitions and checklists that they had developed as clinicians seeing hundreds of patients with the disease they knew as 'ME'. These include
Ramsay's 1986 definition,
Dowsett's London criteria, and
Richardson's 2002 guidelines for doctors. You seem to be more interested in clinical versus research criteria, so I won't bother to mention the Oxford research criteria as it's largely been panned anyways.
In the US, I imagine most doctors use some interpretation of the
CDC case definition to diagnose what they call 'CFS'. As you're no doubt aware, the IOM has come up with
new criteria to diagnose what they are calling 'SEID'. It's not 100% clear whether this definition was meant to encompass both ME and CFS but my interpretation is that it is, unfortunately. I think this is a step backwards and away from the clarity given by the modern ME definitions below.
As
@Snookum96 mentioned, 2003 brought about the
Canadian Consensus Criteria, which could be used to diagnose what they called 'ME/CFS'. In 2011, the
International Consensus Criteria for ME were published. This document advocated for dropping the term 'CFS' entirely and puts forward criteria they believe can be used to diagnose 'ME'. There are probably some US and Canadian doctors, most notably the well known ME/CFS specialists, using the CCC and ICC criteria to diagnose patients, but I imagine the CDC criteria are probably still the most widely used clinical criteria here in North America.
Less well known and talked about, 2007 saw the release of the
Nightingale definition of ME by Dr. Byron Hyde. I imagine nobody other than Dr. Hyde himself uses this criteria, but as you would expect it's meant as an 'ME' criteria. He believes (probably correctly) that ME has nothing to do with CFS.
Beyond these I honestly have no idea what criteria other countries use to diagnose the disease. I imagine some countries don't even recognize it as a real disease still at this point which saddens me.