Construct validity of 2 measures to assess reasons for antipsychotic discontinuation and continuation from patients and clinicians perspectives in a clinical trial

Abstract

Background: Little is known about the specific reasons for antipsychotic discontinuation or continuation from patients or clinicians perspectives. This study aimed to assess the construct validity of 2 new measures of the Reasons for Antipsychotic Discontinuation/Continuation (RAD): RAD-I (a structured interview assessing the patients perspective) and RAD-Q (a questionnaire assessing the clinicians perspective). Methods. Data were used from a 12-week antipsychotic trial of schizophrenia patients in which the RAD was administered at study entry and at study completion (or discontinuation). Construct validity was assessed through comparisons of RAD responses, clinicians responses to a standard patient disposition form identifying reasons for patients study discontinuation, and several standard psychiatric measures. Percent agreement quantified the correspondence between patient and clinician scores. Results: Patients indicating lack of improvement/worsening of positive symptoms as a somewhat to primary reason for medication discontinuation had statistically significantly less improvement in Positive and Negative Syndrome Scale positive score than patients not reporting these as a reason (concurrent validity). Similar results were observed for the RAD negative symptom, functional, social support, and adherence items, whereas the mood and cognitive items were not significantly associated with change scores on standard psychiatric measures. Responses to the RAD were also weakly associated with variables that theoretically should not be related to them (divergent validity). Level of agreement between the clinician- and patient-rated RAD scores was high (60%-100%). Conclusions: Initial validation of the RAD suggests that the instruments are valid tools for gathering detailed information regarding reasons for antipsychotic discontinuation and continuation from patients and clinicians perspectives. © 2012 Faries et al.; licensee BioMed Central Ltd.