Hello Mr XXXXXXX ....
Thanks for your query. Assessment instruments and questionnaires are used more for clinician's convenience and for documentation purposes including medicolegal cases. For eg HAM-D for depression and HAM-A questionnaire for anxiety disorders. It can be used on index visit and follow up visits for prognostication of disease. However, from patient's perspective, a good psychiatric history and complete mental state examination is sufficient to call it a complete evaluation. It is to be noted we have very few lab investigations relevant to psychiatry and none for diagnosis exactly. Hope you found the information useful.
Regards
Dr Sundar
Psychiatrist