Investigations
1st investigations to order
urine drug screen
Test
Substance use has been correlated with the increased incidence of schizophrenia and probably correlates with an increased incidence of schizoaffective disorder. Substance use can also cause psychotic symptoms independent of schizophrenia, as well as exacerbate existing psychosis.
Such screening may need to be repeated periodically.
Result
may be positive if substance misuse present
sexually transmitted disease screening
Test
Treponema infection and HIV infection can cause a variety of psychiatric symptoms. Serum rapid plasma reagin (RPR) test and serum HIV enzyme-linked immunosorbent assay (ELISA) should be ordered in any patient at risk of sexually transmitted disease.
Such screening may need to be repeated periodically.
Result
negative
full blood count
Test
Fatigue, anxiety, depression, and irritability may be associated with abnormalities on complete blood count (e.g., anaemia).
Result
rules out anaemia
thyroid function tests
Test
Fatigue, anxiety, depression, and irritability may be associated with thyroid dysfunction.
Result
rules out thyroid dysfunction
Investigations to consider
laboratory studies to exclude organic causes
Test
Numerous medical conditions can cause psychiatric symptoms. Rarely, herpes simplex virus polymerase chain reaction (HSV-PCR) in cerebrospinal fluid, liver function tests, copper urine level and serum ceruloplasmin, vitamin B12 levels, lupus screen, chromosomal studies, and porphobilinogen tests are used to clarify underlying pathology.
Result
normal
CT/MRI head
Test
Indicated especially if neurological examination is suggestive of pathology. Useful for ruling out cerebral masses. Dementia can also be associated with delusions that can be similar to those present in schizoaffective disorder.
Result
normal
electroencephalogram (EEG)
Test
Rarely indicated, but may be useful in certain situations when there is an atypical presentation or if first-line investigations do not clarify the diagnosis. EEG could help to rule out partial complex seizures that could present with associated mood and psychotic symptoms.
Result
normal
Use of this content is subject to our disclaimer