Reliability/Validity in classification Flashcards
what is inter-rater reliability?
when 2 or more people agree on an observation
how is inter rater reliability measured?
through a kappa score. 0.7 or above is good
what is the kappa score for the diagnosis of SZ?
0.46 (reigers et al)
how did copeland demonstrate cultural differences when diagnosing SZ?
He gave 134 US and 194 UK psychiatrists a description of a patient. 69% of the americans described the patient as schizophrenic, whereas only 2% of the british did.
how did luhrmann demonstrate cultural differences when diagnosing SZ?
interviewed 60 adults diagnosed with schizophrenia and asked about voices they hear: 20 Ghana, 20 india, 20 american.
Most of the african and indians reported positive experiences with their voices (playful and helpful)
None of the americans described positive experiences, but quite negative ones (violent and hateful).
Lurhmann suggested that harsh voices common in the West are not necessarily an inevitable feature of SZ.
what are the 3 issues of validity when diagnosing SZ?
- gender bias
- symptom overlap
- co-morbidity
what is gender bias when diagnosing SZ?
accuracy of diagnosis depends on gender of the patient, due to stereotypical beliefs the clinican may hold about gender. A criticism of the DSM is that some diagnostic categories are biased towards pathologising one gender rather than the other. there is a gender bias on what is considered to be healthy.
Broverman found that clinicians in the US equated mentally healthy ‘adult’ behaviour with mentally healthy ‘male’ behaviour, and so women were more likely to be perceived as mentally unwell
what is symptom overlap when diagnosing SZ?
it refers to the fact that symptoms of a disorder may not be unique to that disorder, but may also be found in other disorders, making it hard to diagnose accurately.
Ellason and Ross (1995) found that patients with dissociative identity disorder (DID) had more schizophrenic symptoms than people diagnosed with actual SZ.
Read(2004) found that most people diagnosed with SZ have sufficient symptoms of other disorders they could also be diagnosed with
what is co-morbidity when diagnosing SZ?
refers to the extent that 2(+) conditions occur simultaneously in a patient. SZ can be with substance abuse, depression or anxiety.
Buckley (2009) estimated that co-morbid depression occurs in 50% patients, and substance abuse in 47%.
A meta-analysis by Swets et al found that at least 12% of patients with SZ also fulfilled the diagnostic critea for OCD, and 25% displayed significant OCD symptoms.
what are 2 limitations of reliability in diagnosis of SZ?
- LACK OF INTERRATER RELIABILITY:
there is little evidence that the DSM is routinely used with high reliability by mental health clinicians. Whaley (2001) found inter-rater reliability correlations in the diagnosis of SZ at 0.11 - UNRELIABLE SYMPTOMS
for a diagnosis of SZ, only one clinical characteristic is needed, if the delusions are ‘bizarre’. however, this introduces new problems. 50 US psychiatrists scored only 0.4 when distinguishing between bizarre and non bizarre delusions. the researchers concluded that this central diagnostic requirement lacks sufficient reliability for it to be considered a reliable method when distinguishing between schizophrenic/non schizophrenic patients.
what is a strength of validity in diagnosis of SZ?
Loring and Powell randomly selected 290 psychiatrists and gave them a couple of descriptions of patient’s behaviour. They were then asked to offer their own judgement using standard diagnostic criteria. If the patient was described as male then 56% diagnosed SZ. If the patient was described as female, then 20% diagnosed SZ.
gender bias was more evident among male psychiatrists, which suggests that accuracy of diagnosis is affected by the gender of both the patient and the psychiatrist.
