SZ 17 Reliability and validity of diagnosis 1

Explain the key concepts of reliability and validity of diagnosis and classification of schizophrenia (5)

* Diagnosis: whether someone has SZ

* Classification: what SZ is

* Reliability: consistency, e.g., inter- rater reliability

* Validity: truth, measures what it is supposed to measure

* i.e., accurate diagnosis of well- defined illness

Identify and define 2 types of misdiagnosis and their effects in the case of schizophrenia (2x3)

* False positive

* Diagnosed with SZ but don't have it

* Unnecessary drug treatment, side effects

* False negative

* Not diagnosed with SZ but do have it

* Lack of treatment

Explain what research has shown about changes in reliability of diagnosis of schizophrenia over time (in 3 'waves') (3x2)

* 1950-70s

* Low reliability due to vague criteria

* 1980s-2010s: moderate reliability due to increased clarity, but subjectivity still a problem

* 2019: high reliability, but only in ideal conditions (time, training and discussion)

* Osorio: +0.97 correlation between doctors in diagnosis

Explain similarities and corresponding differences between DSM and ICD in how they classify / diagnose schizophrenia (2x2)

* Both require 2 symptoms, with a set of core symptoms

* ICD has 1 more on the 'core' list

* Both need 1 month of full symptoms

* DSM needs 6 months of 'signs of disturbance'...

... ICD doesn't

Explain what research (e.g., Cheniaux) has shown about differences in diagnosis of schizophrenia between DSM and ICD, and hence their validity (4)

* Diagnosis rates 2x as high for ICD as DSM

* Due to differences in diagnostic criteria

* DSM underdiagnoses / false negatives / Type 2 errors?

* ICD overdiagnoses / false positives / Type 1 errors?

* At least one of the systems gives invalid results