The American Psychiatric Association are preparing the next edition of the Diagnostic and Statistical Manual of Mental Disorders, due for release May 2013. They are currently testing some of their new criteria in field trials. This involves clinicians using the list of proposed clinical characteristics to diagnose patients. Comparisons are then made between clinicians to see how reliable the diagnoses are i.e. whether clinicians agree on the diagnoses they give.
The field trials use a statistic called kappa where 1 means effect agreement and 0 is agreement may just be due to chance. A few of the current results are kappas of 0.32 for major depressive disorder, 0.2 for generalised anxiety disorder and 0.01 for patients with symptoms of anxiety and depression. A recent article in the New Scientist (‘Diagnosis Uncertain’) reports that leaders of the DSM revision are suggesting that kappas as low as 0.2 should be considered acceptable whereas others dispute this. The end result may be that millions of people end up with erroneous diagnoses.