Totally agree with that. Surely asking the patient if they experience this counts for a great deal- im sure this is the case with other diseases where the aetiology may not be defined and so asking the patient, however 'subjective' this may seem, counts for something. Funny how it all gets so 'complicated' when it comes to ME. Although I don't think PEM is unique to ME- I think there are a few other diseases out there which have this, maybe MS, but not very many. Which makes it all the more important as a defining characteristic.