reliability & validity in diagnosis & classification

what is comorbidity?

the extent that two or more conditions or diseases occur simultaneously in a patient

what is culture?

the rules, customs, morals, childrearing practices, etc, that bind a group of people together and define how they are likely to behave

what is gender bias?

refers to the tendency to describe the behaviour of men and women in psychological theory and research in such a way that might not be seen to represent accurately the characteristics of either one of these genders

what is reliability?

consistency of measurements

what is symptom overlap?

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

what is validity?

whether an observed effect is a genuine one

what are the issues with validity in diagnosis?

• gender bias

• comorbidity

• symptom overlap

what are the issues with reliability in diagnosis?

• culture

what is test-retest reliability?

clinicians must be able to reach the same diagnosis at two different points of time

what is inter-rater reliability?

different clinicians must reach the same conclusion at the same time

what is inter-rater reliability measured by?

a kappa score

what score is a perfect kappa score?

1

what kappa score is considered good?

0.7

what did Regier et al find about the kappa score of schizophrenia diagnosis in the DSM-V field trials?

the diagnosis of schizophrenia had a kappa score of 0.46

what did Jacobson find about the ICD-10 diagnosis of schizophrenia?

concordance rate of 98% for diagnosis

what did Copeland find about cultural differences in diagnosis?

gave 134 US and 194 UK psychiatrists the same description of a patient, 69% of US diagnosed them with SZ and 2% of UK did

what did Luhrmann et al find about cultural differences in diagnosis?

Ghanan & Indian pps reported positive experiences with hallucinations but no Americans did

what is the spiritual model?

where people from certain cultures enjoy or report positive experiences with hallucinations and delusions

how did Lee criticise the view that there are cultural differences in diagnosis?

believes the DSM is objective

how did Lin criticise the view that there are cultural differences in diagnosis?

culture does not play a role because there are more similarities than differences

why might there be gender bias in diagnosis?

• gender-based diagnostic criteria

• clinicians basing their judgements on stereotypical beliefs held about gender

• males tend to suffer more negative symptoms

• females have high level of recovery

what did Broverman et al find about gender bias in diagnosis?

clinicians in the US equated a mentally healthy adult with mentally healthy male behaviour

what other disorders does schizophrenia have symptom overlap with?

• depression

• bipolar

• did

what do Ellason & Ross point out about symptom overlap?

people with DID actually have more schizophrenic symptoms than those diagnosed with schizophrenia

what does Serper say about symptom overlap?

despite symptom overlap between schizophrenia and cocaine abuse, it did not affect validity

what comorbidities are common among schizophrenics?

• substance abuse

• anxiety

• depression

what did Buckley et al estimate about comorbidity?

comorbid depression occurs in 50% of patients and 47% have a lifetime diagnosis of substance abuse

what did Swets et al find about comorbidity between OCD and SZ?

despite them being very rare, 12% of SZ patients have OCD

what are the weaknesses of the reliability of the diagnosis of schizophrenia?

• little evidence that the DSM is used with high reliability - Whaley found inter-rater reliability as low as 0.11 - also seen in Rosenhan’s work - not objective

• unreliable symptoms - only one characteristic symptom is required if delusions are bizarre - Mojtabi & Nicholson - inter-rater reliability correlations of 0.4 when senior psychiatrists asked to differentiate between bizarre and non-bizarre delusions - central diagnostic requirement is not reliable

• cultural and racial differences - prognosis for MEG is more positive - ethnic culture hypothesis - Brekke & Barrio - African American & Latino schizophrenics less likely to experience distress - less symptomatic

what is the ethnic culture hypothesis?

MEG experience less distress associated with mental disorders because of the protective characteristics and social structures that exist in these cultures

what are the weaknesses of the validity of the diagnosis of schizophrenia?

• research support for gender bias - Loring & Powell - male and female psychiatrists read case study - some say male some say nothing - 56% of non gender diagnosed - 20% of male were diagnosed - female psychiatrists showed less gender bias - influenced by both gender of patient and consultant

• consequences of comorbidity - Weber et al looked at 6 million discharge records - many comorbid non-psychiatric - asthma + sz + type 2 diabetes + hypertension - poorer quality of healthcare

• differences in prognosis and outcomes of diagnosis - 20% recover - 10% have lasting significant improvement - 30% show improvement with intermittent relapses - little predictive validity