Reliability and validity

• Reliability (AO1)

  Refers to the consistency of a classification system

  Diagnosis is reliable if a patient is given the same diagnosis on different occasion (Test-retest reliability) or the same diagnosis by different clinicians (inter-rater reliability)
• Reliability (AO3)

  Test-retest reliability occurs when a clinician makes the same diagnosis on 2 separate occasions from the same information

  Read et al reported test-retest reliability to be 37% - low reliability which questions the usefulness of the classification
• Reliability (AO3)

  It has been argued that the classification systems do seem to have improved on inter-rater reliability over time.

  A 2005 study reported 81% agreement using DSM
• Validity (AO1)

  Refers to the extent to which a classification accurately measures what its supposed to measure. Does the diagnosis of schizophrenia represent something that is real and distinct from other disorders.
• Validity (AO1)

  Diagnosis is valid if patient diagnosed with SZ really does have SZ and not another condition

  There are many concerns about validity of classification systems, such as the ICD and DSM do not always arrive at the same diagnosis
• Validity (AO3)

  A study by Cheniaux gave 2 psychiatrists 100 cases and asked them to diagnose patients using ICD and DSM

  Psychiatrist 1 - ICD = 44 and DSM = 26

  Psychiatrist 2 - ICD = 24 and DSM = 13

  Shows poor inter-rater reliability, patients more likely to be diagnosed with SZ using ICD than DSM - problems with validity