Diagnosis: Medical Investigations

Medical investigations help identify conditions that can cause or worsen psychotic symptoms and establish a baseline for treatment. The choice depends on the history and examination. Clinicians may request blood tests, a physical examination or a substance screen when appropriate. Investigations can examine metabolic health, endocrine function or other suspected medical contributors rather than test directly for schizophrenia.

Diagnosing schizophrenia requires a clinical assessment of symptoms, functioning and the course of change. No isolated experience or routine laboratory result establishes the diagnosis. Clinicians consider alternative explanations and interpret findings in the context of development, culture, physical health and personal circumstances.

Brain imaging, electroencephalography and specialised tests are generally guided by particular findings, such as neurological symptoms, seizures, an unusual presentation or rapid changes in awareness. They are not interchangeable screening tests for every person. A normal scan does not rule out schizophrenia, and a group-level brain difference found in research cannot confirm an individual diagnosis. Before antipsychotic treatment, checks may also include weight, blood pressure, glucose, lipids and, when indicated, an electrocardiogram. Explaining why a test is being requested helps distinguish investigation of the symptoms’ cause from monitoring the effects of treatment.

Baseline testing and diagnostic investigation serve different purposes. Glucose and lipid measurements may help monitor treatment safety without explaining psychosis. A neurological investigation may examine a suspected cause. Knowing the question behind a test helps the person understand the result and prevents a normal safety check from being mistaken for proof that no psychiatric or medical difficulty exists.

Further reading: National Institute of Mental Health (1); National Institute of Mental Health (2).