Option - Abnormal 5.2 - validity and reliability of diagnosis

Question 1

Diagnosis

Answer 1

• classifying abnormal behavior on the basis of
  
  • symptoms
  • patient’s self reports
  • observations
  • clinical tests
  • other factors (such as information from relatives)
• Clinicians use diagnostic manuals to make a diagnosis that help classify and standardise it.
• diagnosis involve
  
  • matching results of physiological assessment with classification systems (e.g. DSM-IV-TR and ICD-10)

Question 2

Classification systems

Answer 2

DSM-IV lists mental disorders and its symptoms to diagnose correctly.
- find a treatment for patient and make a prognosis

ICD-10 (The International Classification of Diseases)

- published by WHO
- manual uses term ”mental disorder”
- includes reference to causes of the disorder (etiology)
- may be more culturally sensitive

Question 3

Reliability of diagnosis

Answer 3

• inter-judge reliability
  
  • clinicians should reach same correct diagnosis consistently if using the same diagnostic procedure (think scientific method)
  • e.g. standardized clinical interview, observation of symtoms, neurophysiological examination with scanners and diagnostic manuals
• Reliabilty improved with standardised clinical interview schedules that define and specify sets of symptoms to look for. A subjective interpretation of the severity of symptoms must still be made.
• introduction of diagnostic manuals has increased reliability of diagnosis even though manuals are not without flaws (criticism - if the manuals are incorrect, all the diagnosis will be incorrect. How much do we really know?)
• Reliabilty of diagnosis important for validity. Rosenham (1973) study challenges reliability and validity of psychiatric diagnosis & showed consequences of being called “insane”. Although 8 pseudo-patients were impostors, they were diagnosed with severe psychological disorders.

Question 4

• Cooper et al. (1972) The US-UK Diagnostic Project

Answer 4

• aim:
  
  • investigate reliability of diagnosis of depression and schizophrenia
• procedure:
  
  • Asked American and British psychiatrists to diagnose patients by watching videotaped clinical interviews
• result:
  
  • British diagnosed patients as clinically depressed twice as often
  • American diagnosed patients as schizophrenic twice as often
  • same case did not result in the same diagnosis
  • problems within reliability - cultural differences in interpretation of symtoms and diagnosis

According to Fernando (1991) diagnosis is a social process (clinical assessment, classification and diagnosis) and it is not objective because value judgements are involved. Diagnostic process in psychiatry different from medical diagnosis. Problems in understanding symptoms from individuals in different cultures.

Question 5

Validity of diagnosis

Answer 5

• Validity of Diagnosis receiving the correct diagnosis for correct treatment & prognosis.
• harder to provide correct diagnosis and prognosis for psychological than for physiological disorders as it is not possible to observe signs of the disorder in the same way
• DSM-IV manual includes symptoms but no etiology. Difficult make a valid diagnosis when symptoms relate to different psychological disorders.

Question 6

Mitchel et al. (2009) Meta-analysis of validity of diagnosis of depression

Answer 6

• used data from 41 clinical trials (50,000 patients) that had used semi-structured interviews to assess depression
• general practitioners (GPs)
  
  • 80% reliability in identifying healthy individuals
  • 50% reliability in identifying depression
  • many had problems making a correct diagnosis for depression
  • more likely to identify false positive signs of depression after first consultation
    —> GPs should see patients at least twice before making a diagnosis as accuracy was improved with several examinations over an extensive period
    Evaluation:
    1. strengths of meta-analysis - combines data from many studies; generalize to larger population
    2. weakness - may suffer from publication bias; problems with interpretation as all studies may not use the same definitions

Question 7

Rosenhan (1973) Being sane in insane places.

Answer 7

Aim: test reliability & validity of diagnosis in natural setting, if psychiatrist could differ between “abnormal” and “normal” behavior.
Procedure: Covert ops observation of 8 ops of 5 men and 3 women. Task to present themselves in 12 psychiatric hospitals in US, follow same instructions and report hearing voices.
Result: All pps admitted to psychiatric wards and all diagnosed with schizophrenia and one with manic depression. inside wards they behaved normally before being release after 7 to 52 days with labelled schizophrenia in remission. Follow-up study where staff at ward had to find which patient were impostors. They guessed around 30 patients however there were no impostors.
Evaluation
- sparked off discussion and revision regarding diagnostic procedures as well as consequences of diagnosis for patients
—> development of diagnostic manuals
- raises ethical issues (staff not told about research), justified as results provided evidence of problems in diagnosis
- serious ethical issues in follow-up study since staff assumed impostors to present, but they were real patients and may not have gotten the treatment they needed.