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RHO is employed by Deakin University and is an independent consultant for Measured Solutions for Health P/L; AD is an independent health economist who has received consultancy fees from Janssen-Cilag Pty Ltd; JH, and DKS are employees of Janssen-Cilag Pty Ltd, which markets Risperdal Consta (risperidone long-acting injection) and Invega Sustenna (paliperidone palimitate long-acting injection), RS is the director of PRIMA Consulting Group Pty Ltd, but was employed by Janssen-.Cilag Pty Ltd at the time the study was conducted.
RHO led the design of the study, undertook the statistical analyses, led the manuscript writing, and approved the final manuscript for submission. AD, JH, RS and DKS assisted with the design and interpretation of the study, revised the manuscript and provided approval of the final manuscript for submission.
This study was undertaken to estimate utility values for alternative treatment intervals for long acting antipsychotic intramuscular injections for the treatment of schizophrenia.
Vignettes were developed using the published literature and an iterative consultation process with expert clinicians and patient representative groups. Four vignettes were developed. The first was a vignette of relapsed/untreated schizophrenia. The other three vignettes presented a standardised picture of well-managed schizophrenia with variations in the intervals between injections: once every 2-weeks, 4-weeks and 3-months. A standardised time trade off (TTO) approach was used to obtain utility values for the vignettes. As a societal perspective was sought, a representative sample of individuals from across the community (Sydney, Australia) was recruited. Ninety-eight people completed the TTO interview. The vignettes were presented in random order to prevent possible ordering effects.
A clear pattern of increasing utility was observed with increasing time between injections. Untreated schizophrenia was rated as very poor health-related quality of life with a mean (median) utility of 0.27 (0.20). The treated health states were rated at much higher utilities and were statistically significantly different (p < 0.001) from each other: (1) 2-weekly: mean (median) utility = 0.61 (0.65); (2) 4-weekly: mean (median) utility = 0.65 (0.70); (3) 3-monthly: mean (median) utility = 0.70 (0.75).
This study has provided robust data indicating that approximately a 0.05 utility difference exists between treatment options, with the highest utility assigned to 3-monthly injections.