Reliability And Validity In Diagnosis And Classification Flashcards
What are two issues related to the classification and diagnosis of schizophrenia is reliability.
Reliability and validity
What is reliability
Consistency of measurements
What is inter-rater reliability
the extent to which different assessors will arrive at the same conclusion when diagnosing the same patient.
What happens if schizophrenia is diagnosed inconsistently
It could be problematic as it may be over or under-diagnosed by psychiatrists, meaning patients will be incorrectly labelled as ‘schizophrenic’, or not diagnosed, meaning they won’t receive the treatment they need.
What is validity
the extent to which the classification of ‘schizophrenia’ is a true reflection of the illness the patient is suffering from (does it measure what it intends to measure?).
What is criterion validity
the extent to which using different classification systems produces the same diagnosis in the same patient.
What does it suggest if there are differences in criterion validity
If there are differences here, then it suggests there is a lack of agreement over what schizophrenia actually is.
What is a lack of criterion validity made problematic by?
Co morbidity and symptom overlap
What is co-morbidity
The presence of two different disorders at the same time. If this is common, it may be that the two disorders are actually one disorder, and perhaps should be seen as one condition (for example, schizophrenia and depression).
What is symptom overlap
When two or more disorder share some of the symptoms needed for classification. Schizophrenia and bipolar disorder share many symptoms (such as delusions and avolition), meaning that the same patient could receive two different diagnoses. As with co-morbidity, if disorders share many symptoms it may be more helpful to see them as one disorder.
Evaluation for reliability and validity
- Cheniaux et al and inter-rater reliability
- Buckley et al and problems with validity
- Gender and cultural bias
Evaluation: cheniaux et al and inter-rater reliability
Cheniaux et al (2009) found that inter-rater reliability amongst two psychiatrists was low. One diagnosed 26 out of 100 patients with schizophrenia using the DSM, and 44 out of 100 using the ICD. The other diagnosed 13 using the DSM and 24 using the ICD. This supports that the classification and diagnosis of the disorder is lacking in reliability and validity.
Evaluation: Buckley et al and problems with validity
Buckley et al (2009) found that 50% of schizophrenia patients also had a diagnosis of depression, 29% had a post-traumatic stress diagnosis, and 23% had an OCD diagnosis. This supports that there are problems with validity, namely the issue of co-morbidity.
Evaluation: gender and cultural bias
There is gender and cultural bias present in the diagnosis of schizophrenia. Men are far more likely to be diagnosed, potentially because women are able to cope better with the symptoms, and people of African origin are also more likely to be diagnosed. Perhaps this is due to the cultural significance of ‘hearing voices’, which may be seen by white Western psychiatrists as unusual or bizarre. These factors support that the classification of schizophrenia lacks validity and reliability.
