Diagnosis
The symptoms expressed by a delusional disorder can also be part of a much more serious problem, such as bipolar disorder or schizophrenia, therefore diagnosing the delusional disorder is conducted partially by process of elimination. This occurs because delusions can be part of many other illnesses including dementia, schizophrenia and schizoaffective disorder. They may also be part of a response to physical, medical conditions, or reactions when drugs are ingested.
Interviews are useful tools to obtain information about the patient's life situation and past history to help identifying the delusional disorder. Clinicians may review earlier medical records, with the patient's permission. Clinicians also interview the patient's immediate family. This is a very helpful measure in determining the presence of delusions. The mental status examination is used to assess the patient's memory, concentration, and understanding the individual's situation and logical thinking.
Another psychological test used in the diagnosis of the delusional disorder is the Peters Delusion Inventory (PDI) which focuses on identifying and understanding delusional thinking. However, this test is more likely used in research than in clinical practice.
Read more about this topic: Delusional Disorder