Reliability and Validity of Diagnosis

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Discuss the reliability and validity of Diagnosis

There are many major systems of diagnoses worldwide, including the Diagnostic and Statistical Manual of Mental Health Disorders (DSM), International Classification of Diseases (ICD), and the Chinese Classification of Mental Disorders (CCMD). The DSM is one of the most widely used systems of diagnosis, and has undergone several editions. It is currently in its fourth edition. Diagnosis systems function to categorize and diagnose patients with mental health disorders such as depression, anorexia, schizophrenia and the like. It provides a base for psychiatrists for a diagnosis to be given by listing the symptoms required for specific mental disorders. However, questions have been raised as to whether or not such systems of diagnosis are reliable or valid.

The issue of reliability is one which looks at the question of consistency in diagnosis. Does the DSM or other diagnosis systems provide a consistent guide for psychiatrists to determine psychiatric disorders? There are two types of tests that can be used to gage the reliability of diagnosis systems, inter-rater reliability and test-retest. Inter-rater reliability is the process where two different psychiatrists must give the same diagnosis to the same patient independently of each other, based on the symptoms that they have been presented with using the same classification guide. If the psychiatrists make the same diagnosis, the system is reliable. Test-retest refers to the same patient being given the same diagnosis at different times by the same psychiatrist.

Although the DSM is considered the most famous system of diagnosis, many studies have suggested that it is an unreliable system for diagnosing mental disorders, particularly in the earlier editions of the DSM. For example, Schmidt and Fonda (1956) asked two psychiatrists to diagnose independently 426 patients. There was great variety between the psychiatrists, especially for schizophrenia. (Inter rather reliability was used.) The reliability of diagnosis also varies according to the particular mental disorders that are being observed in patients. Kendall (1974) studied 1913 patients admitted to hospital since 1964, and then readmitted after 1969 (test-retest method). Research showed that schizophrenia was more often rediagnosed as a form of depression than the other way around. There was 70 percent stability in the diagnosis of depression, schizophrenia, dementia and alcoholism but less than 50 percent stability in the diagnosis of anxiety states, paranoid states, and personality disorders. However, this can be argued that the less stable diagnoses can be caused by the subjectivity of anxiety, mainly because it is difficult to assess just how excessive a person’s worries are to be considered a mental disorder. Similarly, a study conducted by Di Nardo et al (1993) studied the reliability of the DSM III for anxiety seeking disorders. Two clinicians separately diagnosed 267 individuals seeking treatment for anxiety and stress disorders. They found high reliability for OCD but very low reliability for assessing generalized anxiety disorder.

Reliability of diagnosis also extends towards cultural differences. Merely by the different diagnosis systems available, such as the Chinese Classification of Mental Disorders (CCMD), cultural bound disorders are considered to exist. Some disorders identified in the ICD-10 and DSM-IV that are not common in China are left out of the CCMD, and others that are included in the CCMB appear to be culture-bond disorders found only within Chinese culture. Even among American and British culture, mental disorders are differently diagnosed. In a study conducted by Cooper et al (1972), American and British psychiatrists watched clinical interviews and were asked to made diagnoses. American psychiatrists diagnosed schizophrenia twice as often, which British psychiatrists diagnosed mania and depression twice as often, thus showing a...
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