|A decision model to compare health care costs of olanzapine and risperidone treatment of schizophrenia in Germany
|Beard A M, Maciver F, Clouth J, Ruther E
This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn.
The study compared the use of olanzapine with risperidone in the treatment of patients with an established history of schizophrenia.
The study population comprised a hypothetical cohort of patients currently suffering from an acute episode of schizophrenia, and who were being considered for first-line treatment with a second-generation atypical antipsychotic. The patients were assumed to have a long-term history of relapsing schizophrenia and to have no other concurrent psychotic diagnoses or other significant health issues. In addition, the patients were assumed to have not received any form of previous treatment with atypical antipsychotics.
The study setting was secondary care. The economic study was carried out in Germany.
Dates to which data relate
The effectiveness data were derived from studies published between 1996 and 2001. The price year was 2002.
Source of effectiveness data
The effectiveness data were derived from a review and synthesis of published data.
The model structure was split into two distinct treatment phases. The first part of the model was a decision tree that reflected an initial 3-month period of acute treatment in which the treatment intent was aimed primarily at reducing the current acute symptoms and stabilising the patient. The second part of the model was a Markov model tracking the longer term treatment experience of the patients. This phase was a prolonged longer term preventive treatment aimed at preventing acute relapses.
Outcomes assessed in the review
The outcomes assessed in the review were:
the clinical response data, defined by a proportional improvement in the Positive and Negative Symptoms Scale (PANSS);
the risk of acute relapse;
the suicide risk; and
the utility values associated with different health states associated with schizophrenia.
Study designs and other criteria for inclusion in the review
The authors reported that data for the model were drawn from pivotal clinical trials of atypical antipsychotics, which were generally based on cohorts of adult patients with schizophrenia who had Brief Psychiatric Rating Scale (BPRS) scores of at least 24.
Sources searched to identify primary studies
Criteria used to ensure the validity of primary studies
Methods used to judge relevance and validity, and for extracting data
Number of primary studies included
Approximately 8 primary studies were included in the review of the literature.
Methods of combining primary studies
The authors did not combine the results of the primary studies. The results from only one study were used to populate an individual model parameter.
Investigation of differences between primary studies
Results of the review
For patients treated with olanzapine, 53.0% achieved an improvement in PANSS scores of at least 30%, 36.8% achieved an improvement of at least 40%, and 21.7% achieved an improvement of at least 50%.
For patients treated with risperidone, 43.6% achieved an improvement in PANSS scores of at least 30%, 26.7% achieved an improvement of at least 40%, and 12.1% achieved an improvement of at least 50%.
The annual relapse rate during the first year of treatment was 19.7% with olanzapine and 23.4% with risperidone.
The annual relapse rate after the first year of treatment was 9.4% with both olanzapine and risperidone.
The suicide risk rate was 13.1% at acute episode.
The suicide completion rates were set to 23%.
The utility weights for the health states were 0.56 for acute symptoms as inpatient, 0.60 for acute symptoms as outpatient, and 0.83 for excellent function as outpatient.
Measure of benefits used in the economic analysis
The health benefit measures used in the economic analysis were the number of quality-adjusted life-years (QALYs) gained. The utility values were derived from a published study (Revicki et al. 1996, see 'Other Publications of Related Interest' below for bibliographic details). The study used a standard gamble approach with clinician assessment.
The direct costs to the health care system were included in the analysis. These included the costs of medications, inpatient hospitalisation, clinic visits (psychiatric, general practitioner, social psychiatric and outpatient), residential home care, residential home care with nursing support, sheltered accommodation, and the default costs of a suicide attempt.
The resource use data were derived from a clinical focus group that comprised four experts (a health economist and three clinical psychiatrists/psychotherapists) with clinical and health economic experience of treating schizophrenia in Germany. Suicide-related costs were derived from an Italian study, as no data specific to Germany were found. Drug doses were based on recommended levels for Germany and an analysis of typical prescribing in Germany using Mediplus IMS data. The unit costs for drugs were derived from German cost data, while the unit costs for other resource use were derived from German health care system sources. Discounting was not relevant, as the costs were incurred during one year, and was therefore not performed. The price year was 2002.
Statistical analysis of costs
The costs were treated as point estimates (i.e. the data were deterministic).
The indirect costs were not included.
The authors undertook a series of one-way sensitivity analyses to investigate the stability of the base-case estimates. The authors varied the absolute difference in relapse rates between olanzapine and risperidone from 5% to 20%. They also varied the alternative hospital admission rates for patients during an acute episode of schizophrenia (range: 50 to 100%).
Estimated benefits used in the economic analysis
The number of QALYs gained when using olanzapine over risperidone was 0.06 per 100 patients.
The costs of treating 100 patients with risperidone were EUR 3,261,334 during the first year of treatment.
The costs of treating 100 patients with olanzapine were EUR 3,226,028 during the first year of treatment.
Synthesis of costs and benefits
The costs and benefits were not combined as olanzapine was found to be both more effective and less costly than risperidone (i.e. it was dominant).
The results of the sensitivity analysis showed that varying the absolute difference in relapse rate between 5 and 20% had no effect on the model results as, under all scenarios, olanzapine was still found to be dominant. In addition, olanzapine remained less costly than risperidone unless hospital admission rates dropped to just below 20%.
The analysis suggested that first-line use of olanzapine has potential cost and clinical benefit advantages over first-line risperidone in atypical naive patients with a history of relapsing schizophrenia.
CRD COMMENTARY - Selection of comparators
The authors conducted a head-to-head comparison of two second-generation oral atypical antipsychotics (i.e. risperidone and olanzapine). Second-generation oral atypical antipsychotics have recently been recommended as first-line treatment for newly diagnosed patients with schizophrenia. You should consider if these two treatments are currently being used in your own setting.
Validity of estimate of measure of effectiveness
The authors did not state that a systematic review of the literature had been undertaken to identify relevant research and minimise biases. They provided only limited details of the review undertaken. The authors used a single study to inform each individual parameter. In some instances the authors reported the reason for using a particular study over others, for example, the study was the most conservative or had the largest study sample. The authors performed a very limited sensitivity analysis of effectiveness data in that they only varied the annual relapse rates. A more extensive sensitivity analysis would have helped demonstrate the reliability of the results.
Validity of estimate of measure of benefit
The estimation of benefits was modelled using a two-part model. The model consisted of a decision tree and Markov model, both of which were appropriate for the study question. The authors provided adequate details of the structure of the model.
Validity of estimate of costs
All the categories of cost relevant to the perspective adopted were included in the analysis. No major relevant costs appear to have been omitted. The costs and the quantities were not reported separately, which will limit the generalisability of the authors' results. Resource use was derived from an expert panel based on schizophrenia experts. The authors performed a limited sensitivity analysis on these assumptions, only the hospitalisation rate being varied. The unit costs were derived from published sources. No sensitivity analysis of the unit costs was performed. Discounting was unnecessary since all the costs were incurred during one year. The price year was reported, which will aid future inflation exercises.
The authors did not make appropriate comparisons of their findings with those from other studies. The issue of the generalisability to other settings was not addressed. The authors do not appear to have presented their results selectively. However, with such a small difference between the two treatment groups in terms of the benefits and costs, the authors should have performed more a thorough and extensive sensitivity analysis. For instance, they could have undertaken probabilistic sensitivity analyses to examine the overall uncertainty in the model parameters.
The authors reported a number of further limitations to their study. First, only direct costs were included; other costs such as impacts on carers and lost productivity were not included. Second, the effectiveness data were derived from clinical trials with tightly defined inclusion criteria, which might limit the generalisability of the results. Finally, the authors assumed that treatment response data could be equally applied in both first- and second-line settings.
Implications of the study
The authors reported that their model could be used to compare a wider set of treatment strategies involving other atypical antipsychotics.
Beard A M, Maciver F, Clouth J, Ruther E. A decision model to compare health care costs of olanzapine and risperidone treatment of schizophrenia in Germany. European Journal of Health Economics 2006; 7: 165-172
Other publications of related interest
Because readers are likely to encounter and assess individual publications, NHS EED abstracts reflect the original publication as it is written, as a stand-alone paper. Where NHS EED abstractors are able to identify positively that a publication is significantly linked to or informed by other publications, these will be referenced in the text of the abstract and their bibliographic details recorded here for information
Revicki DA, Shakespeare A, Kind P. Preferences for schizophrenia-related health states: a comparison of patients, caregivers and psychiatrists. Int Clin Psychopharmacol 1996;11:101-8.
Palmer CS, Revicki DA, Genduso LA, et al. A cost-effectiveness clinical decision analysis model for schizophrenia. Am J Manage Care 1998;4:345-55.
Alexeyeva I, Mauskopf J, Earnshaw S, et al. Comparing olanzapine and ziprasidone in the treatment of schizophrenia: a case study in modeling. J Med Econ 2001;4:179-92.
Subject indexing assigned by NLM
Antipsychotic Agents /economics /therapeutic use; Benzodiazepines /economics /therapeutic use; Decision Support Techniques; Germany; Health Care Costs; Hospitalization /economics; Humans; Quality-Adjusted Life Years; Recurrence; Risperidone /economics /therapeutic use; Schizophrenia /drug therapy /economics /prevention & Suicide /prevention & Treatment Outcome; control; control
Date bibliographic record published
Date abstract record published