Flashcards in Issues Surrounding Classification & Diagnosis Deck (43)
What are the 2 issues regarding the classification and diagnosis of SZ?
Reliability and validity
What is meant by reliability for SZ?
Refers to the consistency of a measuring instrument like a questionnaire to assess the severity of their SZ symptoms
What are the 2 measurements of reliability for SZ?
Inter-rater reliability and test-retest reliability
What is meant by inter-rater reliability for SZ?
Whether 2 independent assessors give similar diagnoses
What is meant by test-retest reliability for SZ?
Whether tests used to deliver diagnoses are consistent over time
Outline inter-rater reliability for SZ
The publication of DSM in 1980 specifically designed to provide a much more reliable system for classifying psychiatric disorders
What is the study associated with inter-rater reliability for SZ?
Outline Carson (91)
Reviewed success of the DSM and claimed it had fixed problem of IRR once and for all - psychiatrists now had a reliable classification system so this should have led to much greater agreement over who did or did not have SZ
Outline test-retest reliability for SZ
Cognitive screening tests like RBANS are important in diagnosis of SZ as they will measure the extent of neurological impairment
What study is associated with test-retest reliability for SZ?
Outline Wilks (03)
Administered 2 alternate forms of tests to SZ patients over interval varying 1-134 days and found TRR correlation of scores across 2 test periods was high at 0.84
Name 5 negative points for the reliability of SZ
1) IRR Whaley (01)
2) Rosenhan (73)
3) Unreliable symptoms - Mojtabi & Nicholson (95)
4) DSM vs ICD - Cheniaux (09)
5) Cultural differences
Outline IRR and Whaley (01) for SZ
Despite claims of increased reliability, over 30 years later and there is still little evidence that DSM is routinely used with high reliability by mental health clinicians - Whaley (01) found IRR correlations as low as +0.1
Outline Rosenhan (73)
Highlighted the unreliability of diagnoses of SZ - 'normal' people presented to psychiatric hospitals in US claiming heard unfamiliar voices in heads saying words like 'empty' 'hollow' and 'thud' - all diagnosed with SZ and admitted - throughout their stay, none of the staff recognised they were actually normal - in a follow-up study, Rosenhan warned hospitals of intention to send out more 'pseudo patients' resulted in a 21% detection rate although non actually presented themselves
Outline unreliable symptoms for the reliability of SZ
For diagnosis, only one of the characteristic symptoms required if 'delusions are bizarre' - Mojtabi & Nicholson (95) got 50 senior psychiatrists in US and asked them to differentiate between bizarre and non-bizarre delusion and produced IRR correlations of only +0.4 hence concluded even this central diagnostic requirement lacks sufficient reliability for it to be a reliable method of distinguishing between SZ and non-SZ patients
Outline DSM vs ICD - Cheniaux (09)
Investigated IRR of diagnoses according t both DSM and ICD and although IRR was above +0.5 for both classificatory systems, SZ more frequently diagnosed according to ICD than DSM criteria
Outline the cultural differences in the classification and diagnosis of SZ
Copeland (73) gave 134 US & 194 British psychiatrists a description of a patient - 69% of US diagnosed SZ but only 2% of British gave same diagnosis thus showing there is massive variation between countries in the diagnosis of SZ
Name and explain a positive point about the reliability of classifying and diagnosing SZ
TTR - measures of cognitive functioning are vital in diagnoses and so must have TTR to be useful - Prescott (86) analysed TRR of several measures of attention and information processing in 14 chronic SZs and found performance of these measures was stable over a 6 month period
What is meant by validity in terms of SZ?
Refers to the extent that a diagnosis represents something that is real and distinct from other disorder and extent that a classification system like the ICD and DSM measures what it claims to measure
What is important to note about reliability and validity in terms of SZ?
They are inextricably linked as diagnoses cannot be valid if it is not reliable
Name the 3 aspects of validity in terms of the classification and diagnosis of SZ
2) Positive or negative symptoms?
What is comorbidity?
The extent that 2 or more conditions co-occur
Outline comorbidity in terms of SZ
Psychiatric comorbidities are common among patients with SZ including substance abuse, anxiety and symptoms of depression - such comorbidity creates difficulties in diagnosis and deciding what treatment
Name the main study associated with comorbidity for SZ
Outline Buckley (09)
Estimate that comorbid depression occurs in 50% of patients and 47% of patients also have lifetime diagnosis of comorbid substance abuse
What is the study associated with positive or negative symptoms for the classification and diagnosis of SZ?
Outline Klosterkotter (94)
Assessed 489 admissions to psychiatric unit in Germany to determine whether positive or negative symptoms were more valid in diagnosis of SZ - found positive symptoms were more useful for diagnosis than negative (these symptoms differentiated the illness from any other disorders)
Outline prognosis for the classification and diagnosis of SZ
People diagnosed as SZ rarely share the same symptoms nor is there any evidence they share the same outcomes therefore diagnosis of SZ has little predictive validity - some never appear to recover but many do
What is the main study associated with the prognosis for the classification and diagnosis of SZ?