Diagnosis, reliability, validity, class systems Flashcards
What determines whether a patient is diagnosed with schizophrenia?
Two or more negative symptoms must be present for at least a month.
What is a classification system?
A group of symptoms of a syndrome with an underlying cause, separate from other disorders.
A diagnostic and statistical manual of mental disorder
Describe the DSM-IV
Developed by American Psychiatric Association.
Used mainly in the US.
Diagnose schizophrenia with an inter-rater reliability of 0.8.
Specifies the presence of one first rank symptom, or two symptoms from a list of positive or negative symptoms.
Minimum duration of symptoms for 6 months, incl. prodromal symptoms and includes deterioration of social functioning.
Dsm-iv schizophrenia has a lower incidence and prevalence rate than icd-10 schizophrenia… therefore a worse prognosis due to the degree of chronicity.
Describe the ICD-10
Developed by World Health Organisation
Used .
Diagnose schizophrenia with an inter-rater reliability of 0.8.
Specifies the presence of one first rank symptom, or two symptoms from a list of positive or negative symptoms.
Minimum duration of symptoms for 1 month.
Explain Reliability
Consistency of symptom measurement and affects diagnosis
There are two ways to measure reliability: Test-retest and Inter-rater
What is test-retest?
Occurs when a clinician makes the same diagnosis on separate occasions using separate information.
What is inter-rater?
Different clinicians make identical, independent diagnosis.
How is inter-rater reliability measured?
by a statistic known as kappa score
1-0
1= perfect inter-rater agreement
0= zero agreement
0.7= considered as good
DSM-V trials for diagnosis of schiz has a score of 0.46. (Reiger et al)
Describe Beck et al
1962
54% CR using inter-rater reliability
among psychiatrists
Assessed 153 patients
Describe Soderberg
2005
81% CR using DSM
shows classification systems to have become more reliable over time
Describe Baca- Garcia
Test-retest
2322 patients in spanish psychiatric hospital between 1922- 2004
assessed 10x = 2/3 kept diagnosis
Describe Jacobsen et al
2005
test-retest
found a concordance rate of 98% among psychiatrists using the ICD-10 classification to diagnose schizophrenia.
Supports sodeberg.
Explain validity into schizophrenia
Concerns how accurate a diagnosis is.
Schiz should be separate from other disorders (e.g. substance abuse etc)
There are three ways to measure:
predictive v
descriptive v
aetiological v
Describe predictive validity
If diagnosis leads to successful treatment, then the diagnosis is seen as valid
Describe descriptive validity
To be valid, patients should differ in symptoms from patients with other disorder (no overlap)
Describe Aetiological validity
To be valid, all schizophrenics should have the same cause for the disorder
Describe Mason et al
The test ability of four different class systems predict the outcome of the disorder (over 13 years) in 99 schizophrenics.
More modern class systems have higher predictive v especially if only symptoms lasting 6 mo considered.
TS= Predictive diagnosis has improved over time, as classification systems improved and updated.
Describe Rosenhan
1973
Aim= test the v of schiz diagnosis using the DSM-II class system
Method= 8 volunteers (no mental health illness)
Presented themselves to different mental hospitals, claiming to hear voices.
all admitted, then started acting normal.
Time taken to be released and reactions are recorded.
Findings= volunteers took 7-52 days to be released, diagnosed as schizophrenics in remission.
normal behaviours= interpreted as signs of schiz.
35/118 actual patients suspected they had schiz.
3 month period= 193 patients admitted.
83 aroused suspicion of them being false patients
Describe Jager et al
Descriptive V
Describe Baillie et al
2009
154 British psychiatrists found that other than an agreement as to the influence of genetics, biochem abnormalities and substance abuse; there are widely different views on the cause of schiz.
Aetiological v of schiz is low.
AO3 - Perfection?- R
Class systems are not perfect
HE they provide practicioners with common language, permitting the communication of research ideas and findings… lead to better understanding
Leads to effective symptoms
Link to eva for antipsychotics
Versions modified over time : DSM-5 and ICD- 10
AO3- Improvement over time- R
more reliable over time (class symptoms)
supported by Jakobsen and soderbeg
TS= benefitting society
AO3- Invalid diagnosis- V
no mention of the cause in class symptoms
no mention of prevalence rates which differ from rural to urban areas
supported by Baillie et al
AO3- Consequences- V
consequences if there is invalid diagnosis
being labelled as a schizophrenic has long lasting negative effect onto the individual
affect social relationship
