Schizophrenia Diagnosis and Permanent Issues

When doing my class room discussion below on the topic of schizophrenia, I particularly appreciated the information in my discussion regarding the differences of the three disorders, noting that schizophrenia often shows a greater number of symptoms, with increased deficit in functioning.

Here is my question to the Brainmass Health Care Experts: Unless it is incredibly clear which disorder is present I wonder if an emergency room is not a great place to place a schizophrenia diagnosis that might end up being something like a substance abuse issue, or injury. I believe that placing that diagnosis on someone when I am unsure would potentially cause permanent problems for the patient. Any input about this?

This is my discussion that I did in class.

Individuals with schizophrenia (ICD-10 F20.9), schizoaffective disorder (ICD-10 F25), and brief psychotic disorder (ICD-10 F23) may present with similar symptoms and therefore it is important to be able to distinguish among the three disorders (American Psychiatric Association, 2013).
Individuals with schizophrenia who present to the emergency room may demonstrate delusions, hallucinations, disorganized speech and behavior, and negative symptoms such as a flat affect, alogia (difficulty speaking, such as due to confusion), or avolition (decreased motivation to perform activities) (American Psychiatric Association, 2013).
Individuals with schizoaffective disorder will, in addition to demonstrating the criteria for schizophrenia, also present with a history of a major mood episode, either depressive or manic. These mood symptoms must be present for the majority of the time that the individual has experienced the illness (American Psychiatric Association, 2013).
Patients with brief psychotic disorder also present with the primary symptoms of schizophrenia, including hallucinations, delusions, and disorganized speech and behavior. However, this disorder resolved within one month (American Psychiatric Association, 2013).
While schizoaffective disorder may be distinguished from the other two by the added component of a major mood episode, the primary distinguishing factor between schizophrenia and brief psychotic episode appears to be time. Thus, it may be difficult to distinguish between these two in the emergency room if the patient has experienced the symptoms for less than one month. However, research suggests that individuals with schizophrenia demonstrate greater numbers and severity of positive and negative symptoms, greater level of disorganized behavior, and greater excitement and emotional distress than individuals with the other two disorders. Thus, patients with schizophrenia possess more severe deficits in functioning (Korver-Nieberg, et al., 2011).