reliability and validity of diagnoses Flashcards
how does diagnosis help professionals and individuals?
- communicates useful information to both professionals and individual
- helps professionals know what symptoms to expect
- aids in identifying appropriate treatments (eg for paranoid schizophrenia)
how does diagnosis ensure comparability and reduce bias?
- ensures comparability among professionals using the same classification system
- DSM IV uses objective behaviours and symptom gets agreed upon by practitioners
- professionals with different backgrounds can still use the same system, reducing bias
why is reliability important in a classification system?
- reliability means consistent diagnoses from different clinicians
- diagnosis is reliable if multiple psychiatrists agree on the same diagnosis for the same individual
what does reliability mean in the context of diagnosing disorders?
- reliability means getting the same results if the process is repeated
- for diagnosis, it means classification system produces the same diagnosis for the same symptoms each time
what is inter-rater reliability in diagnosis?
- inter-rater reliability is when multiple clinicians agree on the same diagnosis for the same set of symptoms
- it measures the extent to which different observers (psychiatrists/psychologists) agree
how have the DSM and ICD systems improved over time?
- DSM V (2013) and ICD-10 (1990) are used globally
- both have been refined with each update
- updates make the systems increasingly reliable
what did Goldstein’s 1988 study show about DSM reliability?
- Goldstein re-diagnosed schizophrenia patients using DSM III and found similar diagnoses to DSM II
- experts also showed high agreement and inter-rater reliability
what did Brown’s 2001 study find about the reliability of anxiety disorder diagnoses?
- Brown conducted two independent interviews with 362 out-patients in Boston
- found good reliability in diagnosing anxiety disorders
what did Beck’s 1961 study show about diagnosis reliability? (weakness + CA)
- Beck found only 54% agreement between two psychiatrists diagnosing 153 patients
- this suggests diagnosis was not very reliable at that time
- newer versions of the DSM since 1961 have shown increased reliability
what did Lipton & Simon’s 1985 study reveal about diagnosis reliability? (weaknesses)
- Lipton & Simon re-diagnosed 131 patients from a psychiatric hospital
- only *516 out of 89** originally diagnosed with schizophrenia received the same diagnosis upon re-evaluation
- shows issues with diagnosis reliability
why is validity important in a classification system?
- classification system must be valid to be useful
- low validity if people with the same diagnosis show different symptoms
- low validity if people with the same diagnosis don’t respond to the same treatment
what does validity in diagnosis mean?
- validity is extent to which the diagnosis is accurate and true
- symptoms of the patient must match those for the disorder
- e.g. in schizophrenia, symptoms like paranoia and auditory hallucinations should be present in others with the same diagnosis
why is diagnosing and predicting the future of a psychological disorder harder than for a physical disorder?
- no objective signs to observe like in physical disorders
- harder to measure or see the disorder directly
- psychological symptoms are based on self-reports or observations
- prognosis is less clear due to the lack of physical evidence
why must a classification system for disorders be reliable and valid?
- reliable: different doctors should agree on the diagnosis
- valid: it must measure what it claims to measure
- if diagnoses differ, the system is not measuring accurately
- DSM and ICD are generally seen as reliable now
what is predictive validity in diagnosis?
- predictive validity means being able to predict the patient’s future behaviour
- helps to know if a person will recover or if symptoms will continue
- a valid diagnosis allows for accurate future predictions about the disorder
what is aetiological validity in diagnosis?
- aetiological validity means the disorder has the same cause for everyone diagnosed
- e.g. if a disorder has a genetic component, family history can support the diagnosis
- ensures the cause of the disorder is consistent across all cases
why is a valid diagnosis important for treatment?
- a valid diagnosis ensures the correct treatment is applied
- the right treatment should be effective for the disorder
- e.g. antipsychotics should reduce symptoms of schizophrenia
what did lee (2006) find about the validity of the DSM-IV-TR criteria for ADHD?
- lee (2006) used a questionnaire with primary school teachers
- teachers’ responses about children’s behaviour matched the DSM-IV-TR criteria for ADHD
- this showed validity of the DSM criteria
what did rosenhan (1973) find about the validity of schizophrenia diagnosis? (weakness)
- rosenhan (1973) tested if psychiatrists could be fooled by faking a symptom
- he found DSM II was not valid
- it couldn’t distinguish between those with a mental disorder and those without
what did jansson (2002) find about the validity of the ICD-10 and DSM-IV?
- jansson (2002) gathered data in Copenhagen using interviews and assessments
- found ICD-10 and DSM-IV had the best agreement in diagnosis (0.823)
- this suggests validity of both systems
what did kim-cohen (2005) study and what were the results?
- studied children with conduct disorder (callous disregard and aggression)
- looked at whether they were more likely to:
- report anti-social behaviour
- be disruptive during assessment
- found that the diagnosis was valid based on their behaviour
why is predictive validity in doubt when diagnosing illnesses?
- each illness might have a recognisable pattern
- but people are different
- pattern may not be exactly the same for every person
- this makes predictive validity uncertain
