Issues with the reliability and validity in classification/diagnosis of SZ Flashcards
What is reliability?
Consistency of research study or measure
What are the 3 AO1 points?
Inter Rater Reliability
Test Retest Reliability
Comorbidity
What are the 8 AO2 points?
Inter Rater Reliability Rosenhans Study Unreliable Symptoms Test Retest Reliability Cultural Diffs Comorbidity and Medical Comps Prognosis Ethnicity and Misdiagnosis
Why was the DSM 3 published?
Create a reliable system for classifying psychiatric disorders
What did the DSM claim to have solved?
The issue of inter-rater reliability
If the DSM has solved the issue of IRR, what should it therefore do?
Minimise conflict over diagnosis of patients
Lead to an increase in agreement
What is a problem with the reliability of the DSM?
- 30 years later, little proof to show it is routinely used by mental health clinicians
What have recent studies shown the reliability of the DSM to be?
IRR as low as 0.11+
Overall, due to the little proof of DSM use and low IRR, what does this show?
- Evidence against use of DSM
- Suggests need for further improvement
- We cannot be certain current edition offers dependable classification
What did Rosenhans classic study illustrate?
Further issues with c/d in terms of its reliability
What happened in Rosenhnans study?
- Normal people recruited to present themselves to P hospital
- All admitted and diagnosed with SZ
In Rosenhans study, how did the ‘normal people’ present themselves?
Claims of unfamiliar voice repeating the words empty, hollow and thud
In Rosenhans study, what did healthcare professionals fail to identify?
Patients were healthy
What happened in Rosenhans follow up study?
- Hospitals warned of intent to send out pseudo patients
- 21% detection rate
Overall, what do the results of Rosenhans study illustrate?
- Even central diagnostic requirement lacks sufficient reliability
- Reinforces need for more reliable classification - more rigorous means of testing?
AO2 What is an issue with the SZ symptoms?
Unreliable
Condition diagnosable with presence of only one characteristic symptom
Sz has unreliable symptoms. What problems has this created for psychiatrists?
Diagnostic issues
Sz has unreliable symptoms. What study illustrated the difficulties this can cause?
- IRR only 0.40+ when 50 US senior psychiatrists asked to differentiate between bizarre/non bizarre
Sz has unreliable symptoms. Overall, what is a problem with this?
- Bizarre is subjective
- Means of diagnosis may be reductionist/over-simplified when we do not fully understand what bizarre is
What does test-retest reliability refer to?
Consistency of tests in delivering diagnoses
Which tests are essential in the diagnosis of SZ?
- Cog screening tests such as RBANs
What do cog screening tests such as Rbans do?
Measure the degree of impairment
What did Wilks do to test the test-retest reliability of cognitive screening tests?
- Alternative forms to test Schizo patients over intervals of 1-134 days
What did Wilks find in his test of alternative RBANs systems?
TRR was high with score of 0.84
Who provided support for the Test-Retest Reliability of RBANs/cog screening classification/diagnosis of SZ?
Prescott
What did Prescott do?
Analysed TRR of several measures of attention/info processing in 14 chronic SZ patients
What did Prescott find?
Stable performance over 6 month period
What do Prescotts findings show?
Results are in favour of test-retest reliability of SZ screening tests as they show consistency over time
What is an issue regarding cultural differences in the reliability of SZ classifications/diagnosis?
Lack of agreement between countries in SZ diagnosis
How has culture challenged the reliability of SZ diagnosis?
Variations between countries
What did Copeland find regarding cultural variations?
- 34 US and 194 British psychiatrists
- Description of patient
- 69% of US diagnosed compared to only 2% of British
What do Copelands findings show?
Evident cultural bias in how SZ is classified and diagnosed
Why might there be cultural diffs in c/d of SZ?
Behaviour in one country seen as normal but a SZ symptom in another
What is validity?
Refers to the extent to which a diagnosis represents something real and distinct from other disorders
What is comorbidity?
- Common in SZs
- Two or more conditions co occur
What conditions might co occur with schizo?
Substance abuse, anxiety, depression
Comorbid depression occurs in how many SZ patients?
50% have depression
47% diagnosed with life-time substance abuse
What can comorbidity create problems with?
Both diagnosis and treatment
What medical complications can comorbidity create?
Poor functioning not due to SZ but other complications instead
What was the study regarding comorbidity/medical complications?
- Analysed 6 mil hospital discharge notes
- Pschiatric/behaviour diagnoses accounted for 45% of cm
- 55% of non-psychiatric diagnoses like diabetes
What is a consequence of co-morbid diagnosis/medical complications?
- Reduces quality of medical care
- Affects prognosis
What do the findings of the comorbidity/medical complications study show?
Importance of differentiating between SZ and comorbid disorders to ensure adequate healthcare
Validity. What is another factor affecting diagnosis?
- Varied outcomes in terms of symptoms
- Patients rarely share the same
What can prognosis vary between?
- 20% recover to previous functioning levels
- Low as 10 or high as 30 though
What does the varying outcomes in prognosis demonstrate?
Very little predictive validity, some recover to greater extent
Why does this happen? Further research
What can affect the outcome in validity of SZ diagnosis?
Ethnicity
What ethnic group shows highest SZ rate in Western countries?
Caribbean
What could the higher prevalence of SZ in caribbean ethnic group be attributed to?
Poor SOL Poor QOL (social isolation) Language barriers, diffs in relating between white patients/black doctors
Why does ethnicity reduce valid diagnoses?
- Diagnostic tools may only be effective to their full extent in some cultural groups
- Developed to accommodate other groups
