Reliability and validity in diagnosis and classification

Question 1

What is reliability in the context of diagnosing and classifying schizophrenia?

Answer 1

Ensuring there is consistency in the diagnosis and classification of schizophrenia by different psychiatrists across time and cultures.

Question 2

What is validity in the context of diagnosing and classifying schizophrenia?

Answer 2

Ensuring that the patient is receiving a correct diagnosis of schizophrenia and that schizophrenia has been correctly classified.

Question 3

What are two factors which brings into question the reliability of diagnosing schizophrenia?

Answer 3

1. Cultural differences
2. Inter-rater reliability

Question 4

What are cultural differences in the context of diagnosing schizophrenia?

Answer 4

There are some positive symptoms of schizophrenia which would be seen as acceptable in African Cultures and would not receive a diagnosis of Schizophrenia (e.g. hearing voices)

Question 5

What is inter-rater reliability in the context of diagnosing Schizophrenia?

Answer 5

The extent to which two or more mental health professionals arrive at the same diagnosis for the same patients.

Question 6

What are 3 factors which bring into question the validity of diagnosing schizophrenia?

Answer 6

1. Symptom overlap
2. Co-morbidity (linked to issues with classification)
3. Gender bias

Question 7

What is symptom overlap?

Answer 7

Symptoms of a disorder may not be unique to that disorder but may also be found in other disorders, making accurate diagnosis difficult.

Question 8

What is co-morbidity?

Answer 8

The extent that two (or more) diseases occur simultaneously in a patient brings into question classification of schizophrenia as if it is commonly found alongside another disorder it may not be a separate condition.

Question 9

What is gender bias in the context of diagnosing schizophrenia?

Answer 9

Accuracy of diagnosis is dependent on the gender of the individual

Question 10

limitations What are the two strengths of reliability of diagnosing schizophrenia? (only A03)

Answer 10

Lack of inter-rater reliability:
Schizophrenia has been shown to have poor inter-rater reliability when it comes to diagnosing it.
Whaley (2001)- found inter-rater reliability correlations in the diagnosis of schizophrenia as low as 0.11 (a score of 1 indicates perfect inter-rater agreement).
Rosenhan (1973)= being sane in insane places:
- ‘normal’ people presented themselves to psychiatric hospitals in the US claiming they heard unfamiliar voice in their head saying the words ‘empty’, ‘hollow’ and ;thud’.
- They were all diagnosed as having schizophrenia and admitted.
- Throughout their stay, none of the staff recognised that they were not actually displaying symptoms of schizophrenia.
- Highlights the unreliability of diagnosis

Cultural differences:
Research suggests there is a significant variation between countries when it comes to diagnosing schizophrenia.
Copeland (1971)- gave US and British psychiatrists a description of a patient. 69% of the US psychiatrists diagnosed schizophrenia, but only 2% of the British ones gave the same diagnosis.
Hearing voices is more acceptable in African cultures because of cultural beliefs in communication with ancestors. When reported to a psychiatrist from a different culture these experiences are likely to be seen as irrational = more likely to be diagnosed with schizophrenia.

Question 11

What are the three limitations of validity of diagnosing Schizophrenia? (only A03)

Answer 11

Gender bias:
This is said to occur when accuracy of diagnosis is dependent on the gender of an individual. It has been found that males are more likely to be diagnosed than females they appear to typically function better than men, being more likely to work and have good family relationships. This high functioning may explain why some women have not been diagnosed with schizophrenia where men with similar symptoms might have been.
Loring and Powell (1988)- Selected 290 male and female psychiatrists to read two case studies of patients’ behaviour and asked to offer their judgement. When the patients were described as ‘males’, 56% of the psychiatrists gave a diagnosis of schizophrenia, whereas when described as ‘female’, only 20% were given a diagnosis.

Symptom overlap:
There is overlap between the symptoms of schizophrenia and other conditions.
Both schizophrenia and bipolar disorder involve positive symptoms like delusions and negative symptoms like avolition. This questions the validity of the diagnosis of schizophrenia.
Under ICD a patient might be diagnosed as a schizophrenic; however, many of the same patients would receive a diagnosis of bipolar disorder according to DSM criteria.

Co-morbidity:
Co-morbidities are common among patients with schizophrenia and this brings into question the extent to which they are separate disorders and not just a single condition (classification of Schizophrenia).
Buckley et al. (2009)- around half of patients with a diagnosis of schizophrenia also have a diagnosis of depression or substance abuse, or OCD. In terms of classification, it may be that, if very severe depression looks a lot like schizophrenia and vice versa, then they might be better seen as a single condition.