Validity and Reliability of Diagnosis

Validity and Reliability of a Diagnosis is vital to understanding a patient and making sure that they are properly cared for. Being able to realize the importance of each aspect it and what affects an invalid or unreliable diagnosis can produce.

            Firstly, how and what is a Diagnosis? In the range of abnormal psychology, it is categorizing and detecting abnormal behavior by means of observing the patient, having clinical tests run, self reports from the patient, and gaining information from others such as relatives. When diagnosing a patient, Clinicians use diagnostic manuals, such as the DSM-IV. These list 300 different “mental disorders” and describe the symptoms but doesn’t explain the cause of it.

            Because of these manuals and means of observations, different clinicians should be able to diagnosis patients similarly, or in other words, with Inter-judge reliability. Also using inter rater reliability, assesses the degree to which several different observers (or “raters”) can give similar estimates to the same idea, can help increase the reliability. In the case of time, using Test- retest reliably assesses the ability of a consistent measure over a period of time.

            In 1973, Rosenhahn created a study that that challenged the psychiatric diagnosis problems by having 8 fake patients and each of them where claimed to have severe psychological disorders even though they were all imposters. A similar study was done by Cooper et al. (1972) just one year earlier named The US-UK Diagnostic Project to examine the reliability of diagnoses made by Clinicians for depression and Schizophrenia. Their method was to have western psychiatrists watch a videotaped interview and provide a diagnosis for the patient. The British psychiatrist diagnosed the patients twice as often and the American Psychiatrists diagnoses the same people with schizophrenia twice as often. Because the diagnoses were not the same, it’s apparent there are problems with reliability.

            The “Validity of Diagnosis” is also extremely important to understanding diagnoses and the patients. The term refers to the correct diagnosis of a patient. The DSM-IV manual doesn’t include causes of disease so it can be hard to make a valid diagnosis.

            In Mitchel et al. (2009), a meta-analysis of validity of diagnosis of depression, used 41 clinical trials with semi-structured interviews to assess depression. The General Practitioners were able to mange 80% reliability to identify healthy patients and 50% reliability in diagnosing depression. They were more likely to make false positive signs of depression during the first meeting with the patient. The study said that GP’s should see patients twice before diagnosing because the accuracy was improved over that time. 

Another study relating to the Validity of diagnosis is Rosenhahn (1973) on being sane in insane places.  5 men and 3 women were to present themselves to 12 different psychiatric hospitals in the US. They all acted normally but all but one was diagnosed with schizophrenia. The other one was diagnosed with manic depression. All though they acted normally through out their stay, the doctors interpreted them taking notes as symptoms of their diagnosis. It took between 7 to 52 days for the 8 pseudo-patients to be released. A follow up was done after this and the study told the doctors that there would be imposters that would present themselves at a hospital. Of the 193 patients who presented themselves, 41 were identified as imposters, 23 were suspected imposters, and one doctor or a staff member suspected 19. None of the identified or suspected patients were imposters. There were none.

Validity and Reliability of a Diagnosis is extremely important because, as in the case of the last study, people who were in fact sick, were thought to be faking. Being able to get a better and more reliable diagnosis will allow psychiatrists to help more people with proper treatments.