Reliability and validity in diagnosis and classification

• What is meant by reliability in terms of diagnosis (referring to schiz)?

  • Consistency of a classification system/of measurement to produce the same data if taken on successive occasions
  • diagnosis of schizophrenia must be repeatable
• what is meant by validity in terms of diagnosis?

  whether an observed effect is a genuine one- a diagnosis that represents something which is real and distinct from other disorders, the extent to which a classification system measures what it claims to measure
• why are validity and reliability inextricably linked in diagnosis?

  because a diagnosis can’t be valid if it’s not reliable
• What is diagnostic reliability?

  A diagnosis of schiz must be repeatable
• what is inter rater reliability measured by?

  a statistic called a kappa score
• what do different kapa scores represent?

  • a score of 1 - perfect inter rater agreement
  • A score of 0 - zero agreement
  • A score of 0.7 or above is generally considered good
• what is the kapa score for the diagnosis of schizophrenia?

  0.46
• What study did Copeland conduct to prove culture has an influence on the diagnostic process?

  • 134 US and 194 British psychiatrists a description of a patient
  • 69% US psychiatrists diagnosed with schiz
  • Only 2% of British ones gave same diagnosis
• What study did Luhrmann et al conduct to prove hearing voices is influenced by cultural environment?

  • Interviewed 60 adults diagnosed with schiz
  • 20 each in Ghana, US and India
  • Each was asked about the voices they heard
  • many of the African and Indian schizophrenics reported positive experiences whereas US ones reported negative experiences with voices- violent and hateful
  • Harsh violent voices may not truly be an inevitable feature of schiz
• What is meant by gender bias in the diagnosis of schizophrenia?

  when the accuracy of a diagnosis is dependent on the gender of an individual
• What is a criticism concerning gender bias of the DSM?

  Broverman et al found clinicians equated mentally healthy adult behaviour with mentally healthy male behaviour. So there was a tendency for women to be perceived as less mentally healthy
• what is symptom overlap?

  refers to the fact that symptoms of a disorder may not be unique to that disorder but may also be found in other disorders, making accurate diagnosis difficult
• two pieces of evidence for symptom overlap?

  • Ellason and Ross said people with DID have more schizophrenic symptoms than people diagnosed with schizophrenia
  • Read- most people diagnosed with schiz have sufficient symptoms of other disorders that they could also receive one other diagnosis
• what is co-morbidity?

  refers to the extent that two or more conditions or diseases occur simultaneously in a patient. psychiatric co morbidities are common in schiz patients
• what did Buckley et al discover about co-morbidity?

  50% of schizophrenics have co morbid depression
• what did Swets et al discover about OCD and schizophrenia?

  • meta analysis
  • 12% of patients with schiz fulfilled diagnostic criteria for OCD as well
  • 25% displayed significant OCD symptoms
• Evaluation of reliability concerning schizophrenia?

  • ☹️lack of inter rater reliability- Whaley found interrater reliability correlations in diagnosis of schiz as low as 0.11
  • ☹️ lack of reliability in diagnosis- Rosenhan and pseudo patients approached psychiatric hospitals and claimed to hear voices saying empty and hollow. All were admitted, behaved normally and were still seen as schizophrenic
  • ☹️ cultural differences- study by Copeland (US and British psychiatrists) and Luhrmann (Asian, Ghanaian and US schizophrenics)
  • ☹️ unreliable symptoms- for diagnosis of schiz, only one of the characteristic symptoms is required if delusions are bizarre, but correlation co-efficient of distinguishing between bizarre and non-bizarre delusions is low (0.4) so this central diagnostic requirement lacks efficiency
• what does the ethnic culture hypothesis state about cultural differences in prognosis? (Estimate of how disease will develop and the chances of recovery/recurrence)

  Ethnic culture hypothesis- ethnic minority groups experience less distress with mental disorders and experience better prognosis due to the social structures of their cultures (Luhrmann et al)
• evaluation of validity associated with the diagnosis of schizophrenia?

  • ☹️ gender bias- loring and powell- 290 male and female psychiatrists to read 2 cases of patients behaviour. 56% gave diagnosis schizophrenia when described as male/no gender info given, only 20% when described as female
  • ☹️ for comorbidity- Weber et al- 6mil hospital discharge cases- psychiatric and non-psychiatric cases of co-morbidity. schizophrenics often experience a lack of medical care, so likely to suffer with other medical problems, affects prognosis
  • ☹️ difference in prognosis- 20% fully recover, 30% show improvement with relapses. Little predictive ability
  • ☹️ symptom overlap- Ellason and ross (DID)
• why are inter-rater and test retest reliability important in diagnosis?

  • test-retest reliability- clinicians must be able to reach the same conclusions at two different points in time on successive occasions
  • inter-rater reliability- different clinicians must reach the same conclusions
• three main aspects of validity related to schizophrenia?

  • gender bias
  • symptom overlap
  • co-morbidity