Table 46

Input parameters utilised in the economic model.

Input parameterDeterministic valueProbabilistic distributionSource of data - comments
Annual probability of relapseDistribution based on 10,000 MTC iterations
95% credible intervals
Olanzapine0.19960.0146 to 0.7222MTC competing risks model - analysis of data included in the guideline systematic review; results for 52 weeks assumed to reflect annual probability; results for placebo assumed to apply to no treatment in all years except the 1st year following the move to no treatment
Amisulpride0.29880.0197 to 0.9042
Zotepine0.10670.0023 to 0.5601
Aripiprazole0.27420.0130 to 0.8531
Paliperidone0.16250.0025 to 0.7008
Risperidone0.27610.0182 to 0.8785
Haloperidol0.33170.0262 to 0.9028
No treatment – following years0.43610.0913 to 0.8613
Flupentixol decanoate0.2977Beta distribution (α=39, β=92 according to data reported in David and colleagues, 1999David et al., 1999. Meta-analysis of trials comparing flupentixol decanoate versus other depot antipsyhcotics; data on relapse
No treatment – first year following discontinuation of treatment0.6062Distribution based on 10,000 MTC iterations– results for placebo, adding the effect of abrupt discontinuation on the risk for relapse (Viguera et al., 1997)MTC competing risks model - a higher probability of relapse over the first 7 months (50%) was taken into account (Viguera et al., 1997)
Probability of discontinuation due to intorelable side effects - 1st year of initiation of a particular antipsychoticDistribution based on 10,000 MTC iterations

95% credible intervals
Olanzapine0.07830.0021 to 0.4784MTC competing risks model - analysis of data included in the guideline systematic review; results for 52 weeks assumed to apply to the 1st year within initiation of a particular antipsychotic only
Amisulpride0.05540.0006 to 0.3721
Zotepine0.38210.0120 to 0.9750
Aripiprazole0.15820.0026 to 0.7847
Paliperidone0.32870.0039 to 0.9770
Risperidone0.09940.0020 to 0.6471
Haloperidol0.09220.0017 to 0.5386
Annual probability of discontinuation due to other reasonsDistribution based on 10,000 MTC iterations
95% credible intervals
Olanzapine0.27300.0207 to 0.8596MTC competing risks model - analysis of data included in the guideline systematic review; results for 52 weeks assumed to reflect annual probability
Amisulpride0.24350.0139 to 0.8324
Zotepine0.22530.0074 to 0.8189
Aripiprazole0.35200.0202 to 0.9218
Paliperidone0.38480.0090 to 0.9479
Risperidone0.17610.0086 to 0.7141
Haloperidol0.25160.0151 to 0.8290
Weight gain - 1st year of initiation of a particular antipsychotic
Distribution based on 10,000 MTC iterations
Odds Ratios versus haloperidol 95% credible intervalsMTC simple random effects model - analysis of data from guideline meta- analysis of side effects; only data reported as “increase in weight gain of ≥7% from baseline” were considered.
Olanzapine2.86311.7050 to 4.5090
Amisulpride1.86040.7345 to 4.0360
Aripiprazole0.73730.3498 to 1.3990
Paliperidone1.07790.4405 to 2.1640
Risperidone1.08950.5214 to 2.0850
Zotepine1.0895As for risperidoneOdds ratio of zotepine versus haloperidol assumed to be equal of that of risperidone versus haloperidol
Probability of weight gain
Haloperidol0.2000Beta distribution (α=31, β=124 according to data reported in studies with time horizon up to 12 weeks included in the guideline meta- analysis of side effects)Extrapolation of data reported in studies with time horizon up to 12 weeks included in the guideline meta-analysis of side effects; only data reported as “increase in weight gain of ≥7% from baseline” were considered.
Flupentixol decanoate0.2000As for haloperidolAssumed to equal that for haloperidol
Acute EPS
1st year of initiation of a particular antipsychotic
Distribution based on 10,000 MTC iterations
Odds Ratios versus haloperidol 95% credible intervals
Olanzapine0.26310.1832 to 0.3641MTC full random effects model - analysis of data from guideline meta-analysis of side effects; only data on “need for anticholinergic medication” were considered
Amisulpride0.39930.2587 to 0.5836
Zotepine0.14760.0517 to 0.3132
Aripiprazole0.25170.1505 to 0.4002
Paliperidone0.29830.1179 to 0.6214
Risperidone0.47430.3680 to 0.5994
Probability of acute EPS
Haloperidol0.5367Beta distribution (α=928, β=801 according to data reported in RCTs with time horizon up to8 weeks included in the guideline meta- analysis of side effects)Extrapolation of data reported in studies with time horizon up to 8 weeks included in the guideline meta-analysis of side effects; only data on “need for anticholinergic medication” were considered
Flupentixol decanoate0.4891Beta distribution (α=45, β=47 according to data reported in David and colleagues, 1999)David et al., 1999. Meta-analysis of trials comparing flupentixol decanoate versus other depot antipsyhcotics; data on need for anticholinergic medication
Following years
Probability of acute EPS - all antipsychotics10% of 1st year estimateN/A (no distribution assigned)GDG expert opinion
Probability of diabetes - 1st year of initiation of a particular antipsychotic Distribution based on 10,000 MTC iterations of data on weight gain Probability of haloperidol estimated from data reported in van Winkel et al., 2006 &2008 and considering the increased relative risk (RR) for diabetes of SGAs versus FQAs; rest probabilities calculated by multiplying respective RRs for weight gain of each SGA versus haloperidol by the probability of diabetes for haloperidol
Olanzapine0.0417Relative risk of each SGA versus haloperidol for diabetes was assumed to equal their in- between relative risk for weight gain; the latter was determined by the posterior distribution of ORs of weight gain for each SGA and haloperidol, respectively
Amisulpride0.0317
Zotepine0.0214
Aripiprazole0.0156
Paliperidone0.0212
Risperidone0.0214
Haloperidol0.0200Beta distribution (α=2, β=98 based on assumption)
Flupentixol decanoate0.0200As for haloperidol
Probability of glucose intolerance - 1st year of initiation of a particular antipsychotic Distribution based on 10,000 MTC iterations of data on weight gain Probability of haloperidol estimated from data identified in the guideline systematic review; rest probabilities calculated by multiplying respective RRs for weight gain of each SGA versus haloperidol by the probability of glucose intolerance for haloperidol
Olanzapine0.3129Relative risk of each SGA versus haloperidol for glucose intolernace was assumed to equal their in-between relative risk for weight gain; the latter was determined by the posterior distribution of ORs of weight gain for each SGA and haloperidol, respectively
Amisulpride0.2381
Zotepine0.1606
Aripiprazole0.1167
Paliperidone0.1592
Risperidone0.1606
Haloperidol0.1500Beta distribution (α=15, β=85 based on assumption)
Flupentixol decanoate0.1500As for haloperidol
Annual transition probability of impaired glucose tolerance to diabetes0.0196Beta distribution
Standard error 0.0025 (Gillies et al., 2008)
Gillies et al., 2008
Annual probability of diabetes complicationsBeta distribution
Determined from the numbers of people experiencing each of the complications at each level of Haemoglobin A1C concentration in the UKPDS (Stratton et al., 2000)
Based on UKPDS data (Stratton et al., 2000), assuming that 20% of people with schizophrenia and diabetes in the model had Haemoglobin A1C concentration 7% to<8%, 30% of people had 8% to <9%, 30% of people had 9% to <10% and 20% of people had ≥ 10%
Fatal myocardial infarction0.0042
Non-fatal myocardial infarction0.0130
Non-fatal stroke0.0039
Amputation0.0023
Macrovascular events-heart failure0.0040
Microvascular events-ischaemic heart disease0.0157
Standardised Mortality Ratio - all cause mortality2.6N/A (no distribution assigned) McGrath et al., 2008
Mortality rates per 1000 people in general population by age25–34 yrs: 0.69
35–44 yrs: 1.29
45–54 yrs: 3.10
55–64 yrs: 7.53
65–74 yrs: 20.48
75–84 yrs: 59.36
≥85 yrs: 164.02
N/A (no distribution assigned)Office for National Statistics, 2008; mortality rates for England and Wales, 2005, estimated based on a male to female ratio 1.4 to 1, characterising people with schizophrenia (McGrath, 2006).
Utility scores Beta distribution
Model health states
Remission0.799Determined using the reported numbers of people valuing each PANSS-generated health state as in Lenert and colleagues (2004)Lenert et al., 2004; linking between model states and states described in the study based on GDG estimates – see text for details. Duration of decrement in HRQoL caused by relapse: 6 months
Relapse0.670
Death0.000
Side effects
Acute EPS−0.888%Estimated from the number of people valuing the presence of each side effect, as reported in Lenert and colleagues (2004)Lenert et al., 2004; acute EPS causes HRQoL reduction corresponding to that of pseudo- Parsokinism, lasting 3 months; weight gain causes permanent reduction in HRQoL
Weight gain−0.959%
Diabetes complications
Myocardial infarction−0.05595% CIs: −0.067 to −0.042Clarke et al., 2002; utility scores based on patient-reported EQ-5D scores, valued using EQ-5D UK tariff values
Stroke−0.16495% CIs: −0.222 to −0.105
Amputation−0.28095% CIs: −0.389 to −0.170
Macrovascular events - heart failure−0.10895% CIs: −0.169 to −0.048
Microvascular events - ischaemic heart disease−0.09095% CIs: −0.126 to −0.054
Annual drug acquisition costs (remission state)N/A (no distribution assigned)BNF 56 (British Medical Association & the Royal Pharmaceutical Society of Great Britain, 2008), except risperidone cost, which was taken from the Electronic Drug Tariff (NHS, Business Services Authority, 2008). Average daily dosage taken from respective NHS data (NHS, The Information Centre, 2008C) and BNF guidance when no other data were available.
Olanzapine£1,036
Amisulpride£696
Zotepine£767
Aripiprazole£1,325
Paliperidone£1,902
Risperidone£821
Haloperidol£175
Flupentixol decanoate£81
Annual costs of remissionGamma distribution
Standard error of all costs: 70% of mean value (assumption)
Details on outpatient, primary and community care cost reported in Table 42; details on costs of residential and long-term hospital care reported in Table 44; 2007 prices
Outpatient, primary & community care£5,401
Residential and long-term hospital care£7,325
Total (cost of antipsychotic medication for relapse prevention excluded)£12,726
Annual costs of relapseGamma distribution
Standard error of all costs: 70% of mean value (assumption)
Details on outpatient, primary and community care cost reported in Table 42; details on costs of treating acute episode reported in Table 43; details on costs of residential and long-term hospital care reported in Table 44; 2007 prices
Outpatient, primary & community care£4,323
Residential and long-term hospital care£5,421
Acute treatment (including olanzanpine)£23,274
Total (cost of antipsychotic medication for relapse prevention excluded)£33,018
Cost of switching between antipsychotics£435Gamma distribution
Standard error: 70% of mean value (assumption)
3 visits to consultant psychiatrist, lasting 20 min each; unit cost from Curtis, 2007 (2007 price)
Cost of treating side effectsGamma distribution
Standard error of all costs: 70% of the respective mean value (assumption)
Details on resource use and unit costs associated with acute EPS and weight gain reported in Table 45; 2007 prices

UKPDS (Curtis et al., 2005); 2007 prices
Acute EPS£177
Weight gain£117
Diabetes (without complications) – annual£199
Fatal myocardial infarction£1,531
Non-fatal myocardial infarction
 first year/following years£5,407/£616
Non-fatal stroke
 first year/following years£3,144/£331
Amputation
 first year/following years£11,238/£401
Macrovascular events-heart failure
 first year/following years£418/£343
Microvascular events-ischaemic heart disease
 first year/following years£363/£271
Discount rate (for both costs and outcomes)0.035N/A (no distribution assigned)Recommended by NICE (NICE, 2008A)

From: 7, Economic model – cost effectiveness of pharmacological interventions for people with schizophrenia

Cover of Schizophrenia
Schizophrenia: Core Interventions in the Treatment and Management of Schizophrenia in Primary and Secondary Care (Update) [Internet].
NICE Clinical Guidelines, No. 82.
National Collaborating Centre for Mental Health (UK).
Leicester (UK): British Psychological Society; 2009 Mar.
Copyright © 2009, National Collaborating Centre for Mental Health.

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