Issues in diagnosis; Reliability Flashcards
Reliability of diagnosis
-This is to do with the consistency of diagnosis
Consistency of diagnosis; Inter-rater reliability
Kleitman’s 3 issues:
- Clinicians subjectivity
- Patients: presentation
- Procedures: classification system
Improvements in reliability
Unreliable diagnosis => invalid diagnoses
Why is reliability necessary but not sufficient for validity of diagnosis?
- Needs to be consistency in diagnosing type 1 and type 2
- If two clinicians give two different diagnoses, then at least one must be wrong
- Not sufficient because diagnosis could be consistent but be wrong
Why are inconsistent classification systems unreliable?
-If different clinicians use different diagnosis systems then this could lead to unreliable diagnosis.
Inter-rater reliability in relation to diagnosis:
-Multiple clinicians need to come to a conclusions with diagnosis, however there issues with subjectivity and the consistency of diagnosis by different doctors.
Consistency of classification
-Range of symptoms; differences between/ convergence of DSM & ICD
Inconsistent classification =>
Inconsistent diagnosis
Inconsistent classification =>
Invalid classification
False positive diagnosis
Can treated for illness they do not have; falsely diagnosed with something they don’t have
False negative diagnosis
Their actual illness can not be treated properly; misdiagnosing their existing illness
Differences in procedures, e.g., use of classification systems
If clinicians use different classification systems or other criteria they are likely to make different diagnoses. DSM is the dominant manual for diagnosis in the US.
- In the past this was a severe problem, as doctors in different societies used very different diagnostic criteria. American and British psychologists were shown the same videotaped clinical interviews and asked to make a diagnosis. The psychiatrists from New York diagnosed schizophrenia twice as often and the London psychiatrists diagnosed mania and depression twice as often (Cooper (1972).
- ICD allows diagnosis with symptoms only within the last month, while DSM insists on some symptoms in the preceding six months. Cheniaux et al (2009) found that rates of diagnosis of schizophrenia using ICD (68/200) were significantly higher than when using DSM- IV (39/200). Cheniaux was able to trace this directly to there being no need for symptoms in the last 6 months in ICD.
Cooper et al.
American and British psychologists were shown the same videotaped clinical interviews and asked to make a diagnosis. The psychiatrists from New York diagnosed schizophrenia twice as often and the London psychiatrists diagnosed mania and depression twice as often
Cheniaux et al.
Cheniaux et al (2009) found that rates of diagnosis of schizophrenia using ICD (68/200) were significantly higher than when using DSM- IV (39/200). Cheniaux was able to trace this directly to there being no need for symptoms in the last 6 months in ICD.
Differences between clinicians; subjective interpretation
Even if the same classification systems are being used, clinicians may interpret them differently. Many phrases in manuals are open to interpretation. For example, in DSM- 5 delusions are defined as bizarre ‘if they are clearly implausible and not understandable to same- culture peers and do not derive from ordinary life experiences’.
