Background: There remains a lack of agreement regarding criteria for treatment-resistant schizophrenia (TRS) and definition of response. Method: A literature search was conducted to identify clinical studies of antipsychotics in TRS using PubMed, EMBASE and PsycINFO (last search 31 July 2011). Psychopharmacological studies with the number of participants of ≥ 40 were evaluated in terms of definitions for TRS and subsequent treatment response. Results: Thirty-three studies of antipsychotics in TRS were reviewed. TRS has been defined mainly by severity in symptoms. Many studies based TRS with at least 2 failed adequate antipsychotic trials (at chlorpromazine equivalent doses of ≥ 1000. mg/day for ≥ 6. weeks), but some studies adopted prospective treatment arm to be certain of sample refractoriness. Treatment response has been defined by a relative change in the representative scales (most commonly ≥ 20% decrease in the Positive and Negative Syndrome Scale), but it sometimes included the absolute criteria such as post-treatment score of ≤ 35 in the Brief Psychiatric Rating Scale or Clinical Global Impression-severity score of ≤ 3 (mild or less severe). Social functioning has not been a primary outcome measure in past pivotal trials, and other important domains of the illness such as cognition and subjective perspectives have not been incorporated into definitions of treatment resistance or response. However, adopting various assessment scales can be time-consuming and complicated, with an additional possibility of disagreement among raters. Conclusion: Defining outcomes in schizophrenia is a challenging task. It is imperative that the field agrees on how this population is better defined and what constitutes treatment response.
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