Diagnosing Schizophrenia in the Initial Prodromal Phase

Abstract

IN THE 1960s, based on longitudinal studies of schizophrenia,¹ the German researcher Gerd Huber described subtle, often only self-perceivable deficits, which were reported not only for the postpsychotic stages in which the patients were examined, but also, retrospectively, for the early course, as "basic symptoms."^2-4 In the Bonn Scale for the Assessment of Basic Symptoms (BSABS),⁵ operational definitions of these prepsychotic deviations are given, along with typical statements of patients and examples of questions, which allow their assessment in a fully or semistructured interview. Besides specific questions, general guiding questions for symptom categories are advised. Based on the patient's description of a complaint, the interviewer decides whether the symptom in question is rated as "present," "questionably present," or "absent." The BSABS has been published in different languages^6-9 (a short English version can be requested from the authors). Furthermore, the BSABS was partially incorporated in other instruments. In 1991, it provided the main source for prodromal symptoms of the Instrument for the Retrospective Assessment of the Onset of Schizophrenia,¹⁰ which was used in a large retrospective epidemiological study of the clinical course of schizophrenia before the first hospitalization.^10-13 Recently, prodromal symptoms as defined by the BSABS were included in 2 early detection instruments of leading work groups in this field: the Comprehensive Assessment of At-Risk Mental States¹⁴ and the Scale of Prodromal Symptoms.¹⁵ The authors of the Comprehensive Assessment of At-Risk Mental States¹⁶ put special emphasis on Huber's distinction between reversible outpost syndromes and continuously progressing prodromes as an important modification of the common concept of prodromes in medicine: because prodromal symptoms can resolve, this means that it does not guarantee transition to a first psychotic episode, but may instead indicate an increased risk of this transition. Thereby, the problem of false-positive predictions¹⁷ is especially important, and an examination of the traditional prodrome concept in prospective studies becomes critical.