Despite no object tests there are diagnostic manuals that highlight the clinical characteristics of the disorder that clinicians can use to inform their diagnosis in attempt to objectify schizophrenia. However, discrepancies exist between the two manuals DSM and ICD. The main flaw is differences between the two. For instance, the DSM specifies that signs of disturbance have to be present for at least 6 months, compared to the ICD which says 1 month. Additionally, the DSM emphasises social impairments as a key symptom whereas the ICD doesn’t acknowledge any social aspects further exacerbating the issues with reliability and validity.
More issues with the diagnostic manuals is interpretation of symptoms is subjective and down the person doing the diagnosis so a great deal of importance is placed on the individual’s ability in diagnosis which may vary between health professionals. Therefore skill, experience and knowledge further affect reliability and diagnosis.
Whaley et al demonstrated this and found inter-rater reliability between health professionals as low as 0.11 in diagnosis. This means when independently assessing patients, the diagnosis was rarely consistent between them. This means that the DSM or ICD tools appears to be unreliable in accurately and consistently diagnosing schizophrenia.
Similarly, Mojabi found a inter-rater reliability off 0.40 when classifying if delusions were ‘bizarre’ suggesting even this diagnostic requirement lacks sufficient reliability to distinguish between those with or without schizophrenia. Therefore, attempting to use ‘bizarre’ as a means to diagnose schizophrenia is reductionistic and simply an attempt to over-simplify something we do not fully understand.
In attempts to improve reliability of the DSM, a number of axis were created relating to different aspects of the disorder as early versions of the manuals were not very reliable. In the early version, key terms were being left interpretable, not clearly defined and different interview techniques were used to assess patients which led to poor reliability of diagnosis between clinicians. The DSM now operationalises its key terms with definitions in attempt to improve the validity of the classifications and remove the subjectivity of different clinicians. Furthermore, a standardised interview technique has been devised called the PSE and a computer program for diagnosis called CATEGO has been devised to eliminate personal bias, further improving the validity and reliability of the classification.
Lastly, classification is prone to cultural bias and lacks cultural validity. For example, Chinese diagnostic criteria excludes certain categories and includes one called neurasthenia which is defined as a weakness of the nerves and is the most frequent diagnoses made in China. It is said they diagnose patients with that instead of schizophrenia as it is socially stigmatise in Eastern culture. The implications of this is that the treatment will not be accurate. This makes data hard to compare based on individuals being diagnosed with different criteria and the differences in treatments if the diagnosis differs.
Further cultural issues were identified in the USA by Cooper et al. He found a rise in diagnosis from 1930s compared to the 1950s, yet rates remained consistent in London. This is because the clinical criteria used in the USA was broader than the UK which makes us question the reliability of the diagnoses.
In conclusion, it is confusing to have several alternative sets of diagnostic criteria, and emphasises the point that all definitions are susceptible to modification and influenced by the political and social contexts. Without this, like Boyle and Bentall suggested, the concept of schizophrenia is neither reliable nor valid and thus the diagnosis is not clinically or scientifically useful. The diagnosis is not valid nor reliable and therefore we need to try and make the current criteria more in line with the ideal criteria if it is to improve.
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