...
Similarly, yes/no questions in A&E might not be answered due to the patient being unconscious - which is a 'normal' happening in A&E. A 'don't know' answer might be prefectly sensible for many questions asked to patients.
What this means for Archetyping
The implications of the above approach for templates are that archetypes should fully model the range of responses for questions and other data elements that may seem to initially be Boolean in nature.
The openEHR Approach
The correct value set should then include yes/no/don't know, and possibly also things like maybe/most likely/unlikely etc. In general, the value set should include values for any possible patient response - the data then correctly show that the patient was asked, but responded with some kind of 'don't know' or did not respond at all. Situations where the information could technically not be obtained, e.g. physician was talking to patient using an internet chat tool and the communication dropped out, or a response was techically impossible for some other reason, e.g. faulty equipment, should be marked with a null flavour. In general, null flavour is used sparingly in openEHR, and is not used for representing typical (if not necessarily common) clinical events that can be observed perfectly well by the clinician.
...