reliability and validity

• What is inter-rater reliability?

  Consistency when two different people measure the same thing. Consistency of diagnoses made by different clinicians when using the same diagnostic criteria for schizophrenia.
• What is test-retest reliability?

  The consistency of measures when the same test is administered to the same person twice.
• What is reliability?

  The extent to which something can produce consistent results through controlled replication.
• Positive evaluations for reliability- strengths

  Jakobsen - Found a 98% concordance rate for Danish patients using the ICD-10 classification. Osorio et al report excellent reliability in over 180 schizophrenic patients using the criteria of the DSM-5: found inter-rated reliability to be +0.97 and test-retest +0.92.
• Reliability limitations

  A major issue with the classification is subjective interpretation.

  Cheniaux et al(2009) had two psychiatrists independently diagnose 100 patients using the DSM & ICD criteria. One psychiatrist diagnosed 26 with schizophrenia using the DSM & 44 using ICD. The other psychiatrist diagnosed 13 using the DSM & 24 using ICD. This suggests poor reliability in regards to the diagnosis of Sz.
• What is validity?

  The degree to which a test measures what it says it measures. How accurate is the diagnosis of schizophrenia?
• What is descriptive validity?

  Refers to the symptoms of a disorder being unique and distinct for another disorder.
• What is predicitive validity?

  Accuracy of predicting the future
• Rosenhan (1973) - limitation


  Found that the diagnosis of schizophrenia lacked validity, and that patients were treated as a reflection of the label they were given, not on their individual symptoms or characteristics .However, finding may no longer be valid as mental health services have now vastly improved since 1973 and errors made by psychiatrists over 40 years ago may now be less likely to happen.
• Fischer and Buchanan (2017) - limitation


  Men are diagnosed with schizophrenia more than women. According to Fischer and Buchanan this could be because men are more genetically vulnerable or because women have better social supports masking symptoms.
• What is comorbidity?

  Where one or more additional disorders occur simultaneously
• Comorbidity limitation

  Buckley et al concluded that schizophrenia is comorbid with depression (50%), substance abuse (47%) and OCD (23%).This suggests that schizophrenia may not exist as a distinct condition, having two disorders at once creates a confusing picture, so weakens the diagnosis and classification of Sz as a distinct condition.
• Cultural bias

  The tendency to over diagnose members from other cultures
• Cultural bias limitation


  Some symptoms such as hearing voices are accepted in some cultures, e.g. Afro-Caribbean societies hear voices from ancestors. Afro-Caribbean men are 10x more likely to be diagnosed as white British men, possibly due to over interpretation by UK psychiatrists. Escobar(2012) - white psychiatrists may tend to over interpret symptoms & distrust the honesty of black people during diagnosis. Afro-Caribbean mean living in the UK appear to be discriminated against by a culturally biased diagnostic system.
• Cultural bias strength

  Cochrane - Afro-Caribbean’s have little immunity to flu and children born to mothers who had flu whilst pregnant have an 88% higher “chance” of developing Sz. Supporting a disproportionate biological cause for the condition within some ethnic minority groups.
• Powell (1988)


  290 male and female psychiatrist to read information about two different patient and give them a diagnosis. When the patient was described as male 56% of the male psychiatrists gave a diagnosis of schizophrenia when the same info was read, but they thought it was a female patient 20% gave the diagnosis of schizophrenia. This difference did not occur when female psychiatrists were asked.
• Symptom overlap


  The perception that symptoms of schizophrenia are also symptoms of other mental disorders.
• Ketter (2005)

  Misdiagnosis due to symptom overlap can lead to years of delay in receiving relevant treatment during which time, suffering and further degeneration can occur. In many cases this has let to suicide.
• Cotton et al - Validity limitation


  Female patients function better than men (e.g. more likely to work and have food family relationships). This suggests some women go undiagnosed and miss out on helpful treatment. The possible under diagnosis of Sz raises questions about the validity of the diagnosis. Practitioner bias-women have better interpersonal skills.