reliability and validity of diagnosis and classification A01

• Classification systems like the one by the DSM-V are worthless unless they are reliable
• Reliability – focuses on the consistency of a measurement and in this case refers to the consistency of classification system such as DSM or a measuring instrument like one used to assess a particular symptom of schizophrenia reliability alone counts for nothing unless the system and scales are also valid
• validity refers to the extent that a diagnosis represents something that is real and distinct from other disorders and the extent that a classification system like DSM measures what it claims it measuresreliability and validity are inextricably linked because a diagnosis cannot be valid if it is not reliable
• Reliability

  ·       Diagnostic reliability means that a diagnosis of schizophrenia must be repeatable so that a clinician using the same classification system with the same patient at 2 different times can give the same diagnosis and if the clinicians are able to do this the classification system is reliable and this is known as test – retest reliability

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• Reliability

  ·       the reliability can also be checked via inter- rater reliability where different clinicians using the same classification system with the same patient must give the same diagnosis and if they are able to then it shows that the classification system is reliable
• Reliability

  ·       inter-rater reliability is measured by statistics called kapa score a score of 1 indicates perfect inter rater reliability and agreement and 0 indicates the opposite (no agreement) a kappa score of 0.7 is generally considered good
• Reliability

  ·       (in the DSM-V field trials by Regier et al in 2013 the diagnosis of schizophrenia had a kappa score of only 0.46)
• This may cause issues with reliability.

  Culture – cultural differences -culture has an influence on the diagnostic process and can affect what is viewed as symptoms of schizophrenia for example malgady in 1987 found a difference in interpretation of hearing voices , costa Rican culture interpreted hearing voices as spirits talking to an individual but in the US hearing voices is interpreted as a symptom of schizophrenia .
• This may cause issues with reliability.

  culture - Copeland in 1971 gave 134 US and 194 British psychiatrists a description of a patient and 69% of Americans diagnosed the patient with schizophrenia whereas only 2% of the British psychiatrist did both of these studies show how cultural differences can affect the inter-rater reliability of these studies show how cultural differences can affect the inter-rater reliability of diagnosis.
• This  may cause issues with reliability.

  Symptom overlap – many symptoms of schizophrenia are the same as other disorders like some negative symptoms of schizophrenia like avolition overlap with symptoms of depression – which means that after looking at a patient’s symptoms one clinician may diagnose schizophrenia, but another may diagnose depression. so, this could be a reason that explains low inter- rater reliability in the diagnosis of schizophrenia and the issue of subjectivity and interpretation.
• things that may cause issues with reliability

  Gender bias – the patient of both he clinical and patient can affect whether a reliable diagnosis is given. Loring and Powell 1988 found that when psychiatrist were asked to diagnose the same people using written cases of patients behaviours they found if the patient was described as male or no information about their gender was given at all then 56% were given a schizophrenia diagnosis however when described as female only 20% were diagnosed as schizophrenic .
• things that may cause issues with reliability

  Gender bias – this gender bias found did not appear to be evident amongst female psychiatrists. therefore, suggests that gender can influence whether a reliable diagnosis is given amongst clinicians (challenges inter-rater reliability)
• things that may cause issues with reliability

  Co- morbidity – this refers to when 2 or more conditions occur together – patients with schizophrenia often also have other disorders like major depressive disorder or bipolar disorder or an anxiety disorder. so, co-morbidity occurs when some symptoms a patient is experiencing are the same across different disorders and this creates a problem for the reliability of a diagnosis as there can be inconsistencies in which disorder is being diagnosed.
• Validity

  Validity refers to accuracy and whether we are measuring what we intend to measure in this case for diagnosis we are measuring if psychiatrist is giving an accurate diagnosis of schizophrenia.
• Validity

  There is 2 types of validity including predictive validity – meaning if a diagnosis is valid then it should lead to effective treatment and we should then be able to predict the prognosis of the disorder there is also descriptive validity , meaning to be a valid , patients with schizophrenia should differ in symptoms from patients with other disorders in some ways
• Issues with validity

  -          - Co morbidity – is when an individual is suffering from one or more conditions at the same time. and this is common amongst schizophrenic patients who may also suffer from anxiety, depression of substance abuse. For example Buckley et al in 2009 estimates that comorbid depression occurs in 50% of patients who suffer from schizophrenia and 47% of schizophrenia patients also have a lifetime diagnosis of co- morbid substance abuse  this theory affects descriptive validity and makes it difficult to diagnosis accurately
• Issues with validity

       - Co morbidity-   schizophrenia and OCD are two distinct psychiatric conditions – with roughly 1% of the population suffering from schizophrenia and around 2-3% developing OCD – so they are both fairly uncommon so we wouldn’t expect the few people with schizophrenia would also develop OCD and vice versa however research suggest otherwise –
• Issues with validity

  co morbidity -evidence actually suggests that the two conditions appear together  more often then you would think and chance would suggest – a meta-analysis by Swets et al in 2014 found that at least 12 % of patients with schizophrenia also fulfilled the diagnostic criteria for OCD and about 25% displayed significant obsessive and compulsive symptoms
• Issues with validity

  - Culture – culture influences the diagnostic process and can affect a diagnosis for example African American and English people of afro – Caribbean origin is more likely than white people to be diagnosed with schizophrenia. as the rates in Africa and west indies are not particularly high this could be because of cultural bias rather than genetic vulnerability. this therefore make predictive validity difficult as if cultures view symptoms differently it is hard to know which is correct.
• issues with validity

  • Gender bias – the gender of a patient can affect diagnosis, usually because or the gender biased diagnostic criteria or a clinician basing their judgements on stereotypes and beliefs about certain genders - for example a male is more likely to be diagnosed with schizophrenia then a female and this may be due to gender bias in diagnosis .
• issues with validity

  • Gender bias – Haye 2011 argues that usually women find it easier to express their feelings, so clinicians are more likely to attribute their symptoms to life events or stress rather than the more serious diagnosis like schizophrenia. this is then likely to leas to poor predictive reliability as an incorrect diagnosis may be mad
• issues with validity

  • Gender bias – critics of the DSM diagnostic criteria are biased towards pathologizing one gender rather than the other. Broverman et al found that clinicians in the US equated mentally healthy adult behaviour to a mentally healthy male and male behaviour – and as a result there was a tendency for women to be perceived as less mentally heathy than men.
• issues with validity -      

      Symptoms overlap – many symptoms of schizophrenia are also found in other disorders, both schizophrenia and bipolar disorder includes symptoms such as delusions and avolition. it may even mean that there is another disorder that incorporates bipolar and schizophrenia or that they are not separate disorders
• issues with validity     

  Symptoms overlap –Ellason and Ross pointed out that people with dissociative identity disorder (DID) actual have more schizophrenic symptoms than people who had actually been diagnosed with schizophrenia , in actual fact most people diagnosed with schizophrenia have sufficient symptoms of other disorders so they could also receive at least one other diagnosis said read in 2004 

  this can then explain low validity in the diagnosis of schizophrenia as without an objective test to diagnose , the wrong diagnosis could be given .