Issues in diagnosis; Validity Flashcards
Valid diagnosis
-A valid diagnosis is one that is accurate and true/ correct.
In order for diagnoses to be correct 2 main conditions have to be satisfied;
- The illness has to be reliably defined / classified and diagnosed
- The illness has to be validly defined or classified
How reliability relates to validity of diagnosis
- If the reliability of diagnosis is poor then so too is the validity.
- If there is inconsistency (lack of reliability) in diagnosis across clinicians at least one must be an invalid diagnosis.
- Reliability is not a guarantee of correctness.
Rosenhan (1973)
Rosenhan’s (1973) study, in which pseudo- patients reported that they were hearing a voice saying ‘thud’ to doctors at psychiatric hospitals. All but one received a diagnosis of schizophrenia. In this case, the doctors were very reliable in their diagnoses, but they were invalid, i.e., wrong; none of the pseudo- patients had schizophrenia.
Major problem
-In Sz there is no physiological indicator of illness; so all psychiatrists can do is observe behaviour
Truth of diagnosis
- Reduced by low reliability
- Improved by increased reliability
- Relies on valid classification system
- Improvements in validity as a result of improvements in reliability?
Invalid diagnosis =>
Wrong treatment
Diagnosis =>
Labelling
Truth of classification
- Is Sz a genuine, distinct disorder?
- Descriptive: do symptoms cluster?
- Aetiological: causes/ mechanisms
- Predictive: prognosis over time
Invalid classification =>
Invalid diagnosis
Swartz
This is shown in Swartz’s case study of an African –American woman who was wrongly prescribed antipsychotics for 10 years to treat hallucinations and agitation. An EEG later revealed evidence of epilepsy, and when the appropriate treatment (anticonvulsants) was given, her symptoms disappeared.
Treatment
If psychiatrists are to treat schizophrenia properly they must be diagnosing it properly. If diagnoses are invalid two errors can occur;
- False positive
- False negative
False positive
- If a patient is diagnosed with an illness that they do not have then they may receive treatment with powerful anti- psychotic drugs
- This may lead to the side effects of anti- psychotics, such as weight gain, sexual dysfunction and tardive dyskinesia
- Some argue that treating people with anti- psychotics when they don’t have Sz can sensitise dopamine receptors and induce the symptoms of Sz
False negative
- If a patient is not diagnosed with an illness that they do have, then they will not receive treatment for an illness that they do have
- This leaves patients vulnerable and suffering unnecessarily
Perlman (2000)
Perlman (2000) reported on patients (who it turned out had Asperger’s syndrome) diagnosed with undifferentiated schizophrenia, but did not fit the criteria properly: they had negative symptoms only. These patients were given unnecessary antipsychotics despite a lack of positive symptoms.