Does change in definition of psychotic symptoms in diagnosis of schizophrenia in DSM-5 affect caseness?

Psychotic symptoms are a central element in the diagnosis of schizophrenia, although their precise definition has varied through the multiple iterations of DSM and the ICD. Schneiderian first-rank symptoms (FRS) have received a particularly prominent position in the diagnostic criteria of schizophrenia since ICD-9 and DSM-III. In the current iteration of DSM (DSM-IV-TR), whereas two characteristic symptoms are ordinarily required to meet criterion A, only a single symptom is necessary if the psychotic symptom happens to be a FRS, notably a bizarre delusion or auditory hallucination of a running commentary or 'conversing voices'. Because of limited data in support of the special treatment of FRS, DSM-5 has made changes to criterion A, requiring that at least two psychotic symptoms be present in all cases with at least one of these symptoms being a delusion, hallucination, or disorganized speech. To assess the impact of these changes on the prevalence of schizophrenia, we examined a research dataset of 221 individuals with DSM-IV schizophrenia to study the prevalence and co-occurrence of various criterion A symptoms. Although bizarre delusions and/or Schneiderian hallucinations were present in 124 patients (56.1%), they were singly determinative of diagnosis in only one patient (0.46%). Additionally, only three of the 221 patients (1.4%) with DSM-IV schizophrenia did not have a delusion, hallucination, or disorganized speech. DSM-5 changes in criteria A should have a negligible effect on the prevalence of schizophrenia, with over 98% of individuals with DSM-IV schizophrenia continuing to receive a DSM-5 diagnosis of schizophrenia in this dataset.

Practicing evidence-based psychiatry. 3. Interpreting treatment guidelines.

Practicing evidence-based medicine (EBM) requires the ability to evaluate relevant evidence for the purpose of making an evidence-based treatment decision. Broadly, there are three available sources of information available to the practicing clinician: individual studies, literature reviews, and practice guidelines. In the first two articles in the series, we described the threats-to-validity (T2V) approach in evaluating evidence and specifically discussed the different threats to validity in applying the findings of a single study or a systematic review to an individual patient. In this article, we describe the elements of a treatment practice guideline and evaluate threats to validity at each of these steps. We illustrate the method by evaluating a practice guideline relevant to the treatment question presented in a clinical vignette. We briefly review practice guidelines for the pharmacological treatment of schizophrenia, discuss recommendations from an exemplar guideline about antipsychotic choice in patients with schizophrenia and consider application of its conclusions to the question of which antipsychotic to select for the particular patient with schizophrenia utilizing the T2V approach.

Practicing evidence-based psychiatry: 1. Applying a study's findings: The threats to validity approach.

One critical skill in the practice of evidence-based medicine is the ability to correctly interpret and apply findings of a study relevant to the clinical question needing to be answered. In this paper, we outline an approach to asking the clinical question in a form answerable by a research study and then finding the most relevant study. We next define the two steps in the process of applying a study's findings towards making a treatment decision and discuss the threats to validity approach. We summarize concepts of statistical conclusion validity, internal validity, construct validity, and external validity. We illustrate the method utilizing a clinical vignette that requires choice of an antipsychotic agent. We discuss the results of Clinical Antipsychotic Trial of Intervention Effectiveness (CATIE) in schizophrenia and consider the threats to the different forms of validity in CATIE.