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Cost-Utility Analysis of Treatment with Olanzapine Compared with Other Antipsychotic Treatments in Patients with Schizophrenia in the Pan-European SOHO Study

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Abstract

Objective

To determine the cost utility of treating schizophrenic patients with olanzapine compared with other antipsychotics in a naturalistic outpatient setting.

Methods

The pan-European SOHO study is a 3-year, prospective, outpatient, observational study of outcomes associated with antipsychotic treatment, focusing on olanzapine, in ten European countries. For the cost-utility analysis, healthcare resource use (inpatient care, day care, outpatient psychiatric consultations and antipsychotic and concomitant medication use) and EQ-5D data were collected at baseline and at 3, 6 and 12 months. The perspective was that of the health service payer. UK healthcare unit costs (year 2004 values) were applied to the resource use data for the ten countries. UK population tariffs were applied to the EQ-5D data to determine utility values.

An Epoch analysis was used to analyze the longitudinal data. Multivariate regression analyses that adjusted for baseline covariates were used to estimate the incremental cost and utility gains for patients treated with olanzapine compared with each of the other antipsychotics (risperidone, quetiapine, amisulpride, clozapine and oral or depot typical antipsychotics).

Results

A total of 10 972 patients were enrolled at baseline, of which 9107 completed the 12-month study period. Treatment with olanzapine was more effective in terms of QALYs gained than all of the other antipsychotic treatments. Treatment with olanzapine dominated quetiapine and amisulpride. The incremental cost for olanzapine compared with risperidone was £226 per patient over 12 months and the incremental cost per QALY gained was £5156, with bootstrap analyses showing 100% of the replications falling below a £30 000 per QALY gained threshold. Compared with treatment with clozapine, olanzapine was found to be marginally more effective, at an additional cost of £13 per patient over 12 months and to have an incremental cost per QALY gained of £775. Bootstrap analyses showed that 81% of replications fell below a £30 000 per QALY gained threshold. Comparing olanzapine with oral and depot typical antipsychotics, the incremental cost was £849 and £1106 per patient over 12 months and the incremental cost per QALY gained was £15 696 and £23 331, respectively. Bootstrap analyses showed that 98% of the replications fell below a £30 000 per QALY gained threshold for the comparison with oral typical antipsychotics, and 79% of replications for the comparison with depot preparations.

Conclusions

Among SOHO patients, if a funding threshold of £30 000 per QALY gained is assumed, this analysis suggests that olanzapine has a high probability of being the most cost-effective treatment compared with other antipsychotic treatments. However, comparison of olanzapine with clozapine and typical depot antipsychotics should be viewed with caution because clozapine is a second-line treatment and depot treatment is used for patients who do not adhere to their oral medication.

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Acknowledgements

The SOHO study is funded by Eli Lilly and Company, Windlesham, Surrey, UK. The SOHO Study Group comprises:

France: J-P. Lepine, Hôspital Fernand Widal, Paris; I. Gasquet, INSERM U 669, Maison des Adolescents, Hôpital Cochin, Paris.

Germany: D. Naber, Universitatskrankenhaus-Eppendorf, Klinik fur Psychiatrie und Psychotherapie, Hamburg.

The Netherlands: C.J. Slooff, Psychosencluster GGX N-Drenthe, Kenniscentrum Scizofrenie, RA Assen.

Spain: J. Alonso, Health Services Research Unit, Institut Municipal D’Investigacio Medica, University of Barcelona, Barcelona; J.M. Haro, Research and development Unit, Sant Joan de Deu-SMM, Sant Boi, Barcelona.

UK: T. Croudace, Department of Psychiatry, Addenbrooke’s Hospital, Cambridge; P.B. Jones, University of Cambridge, Addenbrooke’s Hospital, Cambridge; M. Knapp, PSSRU, London School of Economics, Centre for the Economics of Mental Health, Institute of Psychiatry, London.

The authors thank Mark Belger (Eli Lilly and Company) for his statistical advice and Jo Cooper for her administrative support.

Frank Windmeijer received monetary compensation from Eli Lilly and Company for econometric advice. Martin Knapp and Josep Maria Haro were paid by Eli Lilly and Company for their participation in the SOHO Advisory Board. Stathis Kontodimas, Jacqueline Brown, Mark Ratcliffe and Diego Novick are Eli Lilly employees. Spyridon Tzivelekis was an Eli Lilly employee at the time of submission. Jihyung Hong is working at the London School of Economics as a research assistant and also as consultant for Eli Lilly and Company.

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Authors and Affiliations

  1. Centre for the Economics of Mental Health, Institute of Psychiatry, London, UK

    Martin Knapp

  2. London School of Economics, London, UK

    Martin Knapp & Jihyung Hong

  3. Department of Economics, University of Bristol, Bristol, UK

    Frank Windmeijer

  4. European Health Outcomes Research, Eli Lilly and Company, Erl Wood Manor, Windlesham, Surrey, GU20 6PH, UK

    Jacqueline Brown, Stathis Kontodimas, Spyridon Tzivelekis, Mark Ratcliffe, Jihyung Hong & Diego Novick

  5. Sant Joan de Deu-SSM, Fundació Sant Joan de Déu, Sant Boi de Llobregat, Barcelona, Spain

    Josep Maria Haro

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Correspondence to Jacqueline Brown.

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Knapp, M., Windmeijer, F., Brown, J. et al. Cost-Utility Analysis of Treatment with Olanzapine Compared with Other Antipsychotic Treatments in Patients with Schizophrenia in the Pan-European SOHO Study. Pharmacoeconomics 26, 341–358 (2008). https://doi.org/10.2165/00019053-200826040-00006

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