Who doesn’t have impaired contact with reality? If you said that you didn’t, then you prove my point. To stay on quasi-neutral footing though, there is nothing to say that I am equally as wrong (which seems to show I have some loss of reality). Most things in life are mandated by mankind. There are certain conditions that our biological makeup allow, but the rest of our mental state comes from an expectation of others and/or the perception of the person performing act or non-act.

A healthy mind capable of consciousness shares the same attributes as someone described as psychotic. They both have no credible (objective) means to confirm reality other than their experience; it can’t be transcended and even if it can then the transcendence needs to be objectively confirmed. Does probability prove that if 1 person sees a dollar bill on a desk and others don’t see the dollar bill, that the one individual is out of touch? What if evidence is withheld or another factor alters the view of the 99?

There are three possibilities of alleged people with psychosis and their comprehension of the attribute:

People who think they are normal, but are diagnosed with psychosis
People who think they are psychotic, and are diagnosed with psychosis
People who don’t know or are incapable of rationalizing, and are diagnosed with psychosis

It is put up to an experienced, professional psychologist/psychiatrist whether a person has psychosis or not. I might be getting a little far-fetched, but as a wild thought: what if the psychologist had psychosis? Or the curriculum of abnormal psychology was itself grounded in a psychotic delusion?

Just some thoughts
I think it would be difficult, but if we are to uphold the credibility of scientific conduct, it seems proper to classify things in terms of actual observations than to abstract things further from scientific proof. It might be better to say that Person A is in the minority position, 1-to-99 that a dollar bill rests on the desk. From this, it is induced that he is hallucinating.

Also
What is considered to be an acceptable grasp of reality? Children often are less inclined than adults about many things. That doesn’t mean they are insane. Even normal people sometimes space out or enter irrational states of mind. Complete knowledge is the only reality that doesn’t step into psychosis. Is the use of reality just acceptance and sensational confirmation of popular perception and beliefs?