validity

• validity of diagnosis refers to the accuracy of the diagnosis
• the diagnosis should accurately reflect the symptoms that are being experienced by the patient
• the diagnosis should have predictive validity
• diagnosis of schiz lacks predictive validity as the outcomes vary between patients (rule of thirds)
• patients can receive different diagnosis depending on the assessment system used as there are different diagnostic criteria in the ICD and DSM.
• cheniaux (2009) found that schiz is more likely to be diagnosed using the ICD than the DSM
• the differences in diagnostic criteria (between ICD and DSM) suggest that schiz is over-diagnosed using the DSM or under-diagnosed using the ICD.

  this indicates poor validity as patients aren't receiving accurate diagnosis and treatment.
• the diagnosis of schiz is also criticised for lacking predictive validity
• the outcomes vary greatly between patients with roughly a third of the patients having one episode, a third having an episodic pattern or remission and schizophrenic episodes and a this who have no remission
• the symptoms experienced will vary greatly between patients with a diagnosis of schizophrenia

  • e.g. som e will display positive symptoms of schiz which is very different from those displaying negative symptoms but both receive the same diagnosis of schiz
• differences in the diagnostic criteria given in the ICD and the DSM mean that patient can receive a different diagnosis depending on the assessment system used
• CHENIAUX et al found that schizophrenia is much more likely to be diagnosed using the ICD than the DSM

  suggesting that either schiz is over-diagnosed with ICD or under-diagnosed with DSM, which indicates poor validity, leading to patients not receiving an accurate diagnosis and treatment