Personal evaluation of transitions in treatment (PETiT):a scale to measure subjective aspects of antipsychotic drug therapy in schizophrenia

Abstract 

The paper describes the development and preliminary testing of a scale designed to capture aspects of subjective responses to, and tolerability of antipsychotic drugs, treatment adherence, and impact of antipsychotic drug therapy on the quality of life of individuals treated for schizophrenia. Using empirical study approaches and qualitative methods of data analysis, twelve themes were initially identified as relevant to the quality of life of individuals during antipsychotic drug therapy. Based on these dimensions, in the second phase, a 30 item self report questionnaire was constructed and field tested in a community based, heterogeneous sample of schizophrenic patients (n=335). The scale was easy to self-administer (in 2–5min) and perceived as user-friendly by patients. Correlational analysis revealed a high internal consistency (Cronbach's alpha=0.92) and split half reliability (Spearman–Brown coefficient of 0.85). The scale scores were able to distinguish subjects with lower and higher rates of treatment adherence, and factor analysis confirmed the robustness of the original construct. Repeated administration of the scale in a sub-sample of clinically stable schizophrenic population (n=71) revealed a test–retest reliability coefficient of 0.97 (P<0.001); and repeat administration at quarterly intervals in a sample of patients receiving active treatment (n=54) indicated a significant increases in mean scores (t=6.2, df=53, P<0.005), suggesting that the scale was sensitive to changes in patients’ clinical status. Based on these preliminary data, PETiT could be considered as a potentially useful tool for measuring client-centred outcomes in clinical practice, drug trials, quality assurance programs and interventional research involving schizophrenic patients.

Keywords:  Subjective tolerability, Schizophrenia, Outcome measures, Antipsychotic drugs, Clinical trials, Quality of life