Reliability and Validity of Diagnosis

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Created by: chloeairton1
Created on: 12-03-15 14:45

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Reliability and Validity of Diagnosis
- Reliability
  - Inter-rater
    - Consistency in diagnosis between two clinicians looking at the same patient
  - Test re-test
    - Repetition of a diagnosis assessed by testing the same person twice with a gap of weeks or months and diagnosis should be the same
  - Beck et al (1962)
    - The agreement on diagnosis for 153 patients between two psychiatrists was only 54%
  - Cooper et al (1972)
    - NY psychiatrists 2x as likely to diagnose schiz - London psychiatrists 2x as likely to diagnose mania or depression
  - Brown
    - 67% agreement rate for major depression
  - Davison and Neale (1994)
    - 92% agreement rate for psychosexual disorders, but only 54% for somatoform disorders
  - Zigler and Phillips (1961)
    - 54-84% agreement rate when looking at various mental illnesses
  - Nicholls et al
    - Compared reliability of DSM IV, ICD 10 & The Great Ormond Street's classification system for children with eating disorders
      - ICD - 36% agreement DSM - 64% GOS - 88%
- Validity
  - Criterion
    - When two or more diagnostic systems agree with each other e.g. DSM and ICD-10
  - Concurrent
    - Symptoms that form part of the disorder but are not part of the actual diagnosis, should be found in the diagnosed e.g. people with schizophrenia having poor personal hygiene
  - Etiological
    - A group of people who have been diagnosed with the same disorder will have the same factors causing it e.g. schiz - excess dopamine
  - Predictive
    - If diagnosis can lead to a prediction of future behaviours caused by the disorder
      - E.g. the drug lithium carbonate is effective for bipolar disorder but not other mental disorders. If a classification system has good predictive validity and diagnoses someone with bipolar, they should respond to lithium carbonate
  - Nicholls et al
    - Lacked criterion validity when diagnosing as DSM, ICD and GOS didn't agree- 50% couldn't be diagnosed using DSM
  - Kim Cohen et al (2005)
    - Predictive validity - predicted the children who were diagnosed would show behavioural and educational difficulties at 7
  - Lee (2006)
    - High criterion validity - the DSM, ADHD test and teacher assessments matched in their diagnosis