Diagnosis and Classification

• Diagnosing Schizophrenia


  International Classification of Disease (ICD-10)

  Diagnostic and Statistical Manual (DSM-5)
• DSM-V (DSM-5) Criteria


  1. Two or more characteristic symptoms
  2. Social/occupational dysfunction for long period of time
  3. Duration - at least 6 months
  4. Schizoaffective disorder, depression or bipolar disorder ruled out
  5. Disturbance not attributable to substance abuse
• Positive Symptoms


  An additional experience beyond the ordinary.

  Hallucinations:

  • unusual sensory experiences

  Delusions:

  • irrational beliefs - paranoia, grandeur (superpowers), reference (personal messages)
• Negative Symptoms


  The reduction or loos of usual abilities and experiences

  Speech poverty:

  • reduction in amount and quality
  • difficulty producing words

  Avolition:

  • apathy = lack of interest, enthusiasm
  • reduced motivation
  • poor hygiene and grooming, lack of work or energy
• Reliability and Validity


  Reliability

  • Consistency to assess particular symptoms of schizophrenia
  • Clinicians must reach same conclusion at 2 different points in time (test-retest) and there should be consistency between diagnosis (inter-rater)

  Validity

  • A diagnosis represents something real and distinct from other disorders
  • Classificatory system measures what it intends to
• Reliability : Research


  Whaley - found inter-rater correlations for DSM-3 as low as +0.11

  Osorio et al - found inter-rater reliability of +0.97 and test-retest reliability of +0.92
• Validity : Research


  Osorio et al - excellent agreement between clinicians when they used measures from the DSM system
• Co-morbidity


  The extent that two or more conditions co-occur

  Buckley et al:

  • 50% with schizophrenia also have depression
  • 47% have substance abuse
  • 23% have OCD

  Validity of classification - schizophrenia may not exist as a distinct condition

  Validity of diagnosis - some people diagnosed may have unusual cases of other conditions
• Symptom Overlap


  Symptoms of a disorder may not be unique and found in other disorders.

  Ellanson and Ross:

  • People with DID have more schizophrenic symptoms than people with schizophrenia

  Validity of classification - schizophrenia and DID may be variations of a single condition

  Validity of diagnosis - very difficult to diagnose as hard to distinguish
• Gender Bias


  Loring and Powell

  • 56% psychiatrists gave diagnosis when patient was described as male or no gender given. Only 20% diagnosed when same patient was described as female. Only evident in male psychiatrists.

  Reliability and validity - under-diagnosis means women may not be receiving treatment and services they need
• Culture Bias


  Copeland

  • 69% of US psychiatrists diagnosed schizophrenia compared to only 2% of British psychiatrists using same patient

  Reliability and validity - under/over diagnosis of patients in different countries