There were two components to the cost-effectiveness analysis. The primary analysis was an analysis alongside the RCT described in Chapters 3 and 4. The secondary analysis was a decision model, using trial data to project the costs and quality-adjusted life-years (QALYs) associated with ERP therapy and psychoeducation over 10 years. The decision model includes a synthetic arm so that the potential costs and QALYs of a face-to-face CBIT could be incorporated into the analysis. CBIT is considered to be the ‘gold standard’ treatment for tics but is not currently widely available in the NHS in England.
Cost of the intervention
The intervention cost is made up of two components. Firstly, there is the BIP platform, which delivers the ERP intervention. Secondly, there is the therapist time cost to support the delivery of the intervention. Therapist time was available in the ERP therapy as well as in the psychoeducation arm.
Cost of the BIP platform
The cost of the BIP platform is split into a fixed cost per participant and a variable cost based on platform use.
Fixed cost
A yearly cost of the platform was provided by the Swedish team in SEK. This was translated into Great Britain pounds (GBP) using the exchange rate at the time of the analysis (September 2020). This cost is divided by the number of participants in the intervention group to a conservative estimate of the fixed cost per participant: it is likely that there will be a higher caseload of people using the platform if it were to be rolled out and hence it is likely the cost per patient would be less in such circumstances.
Variable cost
Every time a participant logs in to the BIP platform they are sent a text message. To account for this an average of the cost of sending a text with different UK network providers has been calculated. This has then been multiplied by the number of logins to the platform by participants and their supporters.
Cost of delivering therapist support
The cost of therapist support is also broken down into a fixed and variable cost.
Fixed cost
The fixed cost of therapist support is made up of the cost of training and supervision for the therapists. Most of the therapists were trained in supervision, which occurred every week over the course of the intervention for 1 hour. The hourly cost of therapists and those providing supervision is used to calculate the total cost of supervision and training. This cost is also divided by the number of participants in the intervention arm to provide an average fixed cost of therapist support per participant. It is also likely that this is a conservative estimate (the true cost per patient is likely to be less as the number of patients per therapist may be higher in the real world).
Variable cost
Total therapist time per participant is collected as part of the platform. This is broken down into therapist time for the child, parent 1 and parent 2 and phone time with the therapist for the child, parents and parents and child together. A patient-level variable cost of therapist support is calculated for each participant based on therapist time reported and the grade of the therapist they are reported to have interacted with.
Economic evaluation methods
Perspective, discounting and time horizon
In line with NICE Technology Assessment guidelines,80 both the primary analysis alongside the RCT and secondary decision model analysis took an NHS and personal social services cost perspective. A secondary analysis from a wider societal cost perspective was also conducted for the analysis alongside the RCT. All costs and QALYs after 12 months were discounted at a rate of 3.5% per annum.80 The analysis alongside the RCT reports costs and QALYs at 6 and 18 months to take into account the naturalistic observation that occurs after 6 months. The decision model has a time horizon of 10 years.
Outcome measures
Both the analysis alongside the RCT and the decision models estimate costs and QALYs.
The primary outcome measure was the incremental cost-effectiveness ratio (ICER), calculated as the mean incremental cost per QALY gained calculated from the parent-completed CHU9D at 18 months.
The analysis alongside the RCT also reports the incremental cost per change in YGTSS-TTSS.
Primary analysis: analysis alongside the RCT
The analysis alongside the RCT incorporated the costs incurred and health benefits accrued over the 18-month time horizon of the trial. All statistical analysis was conducted in Stata version 17.81
Costs and resource use
The costs that each young person incurred included the cost of the intervention, including the cost of the BIP platform for each participant randomised to ERP therapy, and the cost of delivering therapist support for both ERP therapy and psychoeducation groups (see above) and resource use collected during the trial using an adapted version of the CA-SUS.82–84
The primary analysis was from a health and social care cost perspective. Resource use was collected on specialist tic services, contacts with professionals in the community, inpatient contacts, emergency contacts and medication use at baseline and at 3, 6, 12 and 18 months asking about resource use since last follow-up or in the previous 3 months at baseline using the CA-SUS. Unit costs used in the health and social care cost perspective analysis are reported in Table 15 and are in 2019 GBP.
| Item | Unit cost (GBP) | Source |
|---|---|---|
| Tic disorder clinic | ||
| Specialist assessment | 949 | Cost provided by clinicians at GOSH and NHCFT |
| Treatment session in clinic | 67 | Cost provided by clinicians at GOSH and NHCFT |
| CAMHS | ||
| Multidisciplinary team | 119 | Cost from PSSRU 2016 adjusted using NHS cost inflation index |
| Paediatrician (hospital) | 180 | Average of consultant- and non-consultant-led hospital paediatrician from PSSRU 2019 |
| Paediatrician (community) | 176 | Average of consultant- and non-consultant-led community paediatrician PSSRU 2019 |
| Child and adolescent psychiatrist | 292 | Weighted average of child and adolescent psychiatry national reference costs 2019 |
| Neurologist | 109 | Medical consultant, hospital-based doctors (PSSRU 2019) |
| Psychologist | 54 | Band 7 community-based clinical psychologist (PSSRU 2019) |
| Speech and language therapist | 54 | Band 7 community-based speech and language therapist (PSSRU 2019) |
| Occupational therapist | 45 | Band 6 community-based occupational therapist (PSSRU 2019) |
| Rheumatologist | 354 | Paediatric rheumatology (national reference costs) |
| ENT | 105 | Weighted average ear, nose and throat attendances (national reference costs) |
| Geneticist | 368 | Geneticist (national reference costs) |
| Counsellor | 54 | Band 7 community scientific and professional staff (PSSRU 2019) |
| School counsellor | 49 | School-based children’s health services (PSSRU 2019) |
| School-based speech and language intervention | 91 | Average of group-based and one-to-one session (PSSRU 2019) |
| School nurse | 59 | School-based children’s health services (PSSRU 2019) |
| Podiatry | 67 | Weighted average podiatry attendances (PSSRU 2019) |
| Cardiologist | 179 | Weighted average paediatric attendances (national reference costs) |
| Psychiatric nurse | 55 | Nurse (mental health clinic) (PSSRU 2019) |
| Orthotic services | 86 | Weighted average orthotics attendances (national reference costs) |
| Orthopaedics | 128 | Weighted average paediatric orthopaedics (national reference costs) |
| Dentist | 133 | Dentist patient contact (PSSRU 2019) |
| Endocrinologist | 228 | Weighted average paediatric endocrinologist (national reference costs) |
| GP | ||
| Clinic | 39 | 9-minute GP appointment (PSSRU 2019) |
| Nurse (GP practice) | ||
| Clinic | 6 | 10-minute GP nurse appointment (PSSRU 2019) |
| Social worker | 50 | Children’s services (PSSRU 2019) |
| Special education needs coordinator | 21 | Cost per hour based on average salary from National Careers Service, 37-hour work week and 46.4 working weeks per year |
| Educational psychologist | 54 | Band 7 community psychologist |
| Parental group | 26 | Average of cost per session from different parental groups in PSSRU 2019 |
| Play/art/music/drama therapist | 54 | Band 7 art therapist in community-based scientific and professional staff (PSSRU 2019) |
| Physiotherapist | ||
| Group session | 81 | NHS costs for children’s health services (PSSRU 2019) |
| One-to-one | 100 | |
| Dietitian | 90 | National reference costs |
| Osteopath | 40 | NHS England website on osteopaths |
| Orthodontics | 137 | Weighted average of orthodontic attendances (national reference costs) |
| Eye specialist | 117 | Paediatric ophthalmologist (national reference costs) |
| Urologist | 133 | Weighted average of urology attendances (national reference costs) |
| Paediatric inpatient stay | ||
| Rotavirus complications | 566 | Weighted average of paediatric gastroenteritis elective inpatient attendances (national reference costs) |
| Minor injuries | 1032 | Weighted average of paediatric minor injury inpatient attendances (national reference costs) |
| Cardiology | 1551 | Weighted average of paediatric cardiology inpatient attendances (national reference costs) |
| Accident and emergency | 218 | Weighted average of accident and emergency attendances (national reference costs) |
Wider societal costs include out-of-pocket costs, the cost of education support, voluntary services and the cost of days off from school, also collected using the CA-SUS. When reporting days off from school we report total days off as well as the number of days off that participants attributed as being related to TS.
Out-of-pocket costs are calculated using the amount reported by parents in the CA-SUS. The costs of days off from school are calculated using a human capital approach based on the cost of child care for each day a participant has reported taking off school. Unit costs used in the wider societal cost perspective analysis are reported in Table 16 and are in 2019 GBP.
| Item | Unit cost (GBP) | Source |
|---|---|---|
| Education support | ||
| Individual tuition at home | 31 | Per-hour average collected from survey of 2000 tutors run by ‘thetutor.com’ |
| Individual tuition in a special unit | 21 | Cost per hour based on average annual salary from National Careers Service (NCS), a 37-hour work week and 46.4 working weeks in a year |
| Education welfare officer | 18 | Cost per hour based on average annual salary from NCS, a 37-hour work week and 46.4 working weeks in a year |
| Classroom assistant | 9 | Cost per hour based on Office for National Statistics (ONS) Standard Occupational Classification (SOC) 2019 weekly wage and a 37-hour work week |
| Support from learning mentor | 9 | Cost per hour based on ONS SOC 2019 weekly wage and a 37-hour work week |
| Voluntary services | ||
| Tourettes Action | 10 | Unit cost for any average contact provided by Tourettes Action |
| Day care centre | 38 | PSSRU 2019 cost per day |
| Early years support worker | 10 | Cost per hour based on average annual salary from NCS, a 37-hour work week and 46.4 working weeks in a year |
| Local self-help group | 26 | Assumed cost to be the same as parent support groups in the community |
| Days off school | 83 | Daily wage of a childminder based on ONS SOC 2019 |
Utilities
Health-related QoL utility tariffs are calculated from responses to the CHU9D,85 a child-specific patient-reported outcome measure validated for use in the calculation of QALYs and applying the algorithm developed by Stevens.86 NICE does not recommend specific measures of HRQoL in CYP but that the choice of measure should be informed by evidence of psychometric performance, evidence that it is valid in the age ranges being studied and the quality and availability of value sets. The CHU9D has been validated for use in child and adolescent mental health services, is designed for those aged 7–17 years in line with our inclusion criteria and has a UK value set.
The CHU9D was completed as a patient-reported outcome by the young person and a proxy reported outcome asking about the young person completed by a parent/carer at baseline and at 3, 6, 12 and 18 months. The parent-completed version of the measure was pre-specified as the primary analysis in the health economics analysis plan (HEAP) based on the assumption that we would have better completion rates for the parent-completed rather than young person-completed version.
Cost–utility analysis
Analyses were pre-specified in the HEAP.
We calculated complete case descriptive statistics for the percentage of participants that used each type of resource and the mean number of contacts for the participants that used them. The mean difference in costs and 95% CIs for each resource use type was calculated using regression analysis adjusting for baseline costs, with site as a covariate and bias-corrected bootstrapping with 1000 iterations for complete cases (complete resource use at baseline and at 3-, 6-, 12- and 18-month follow-ups).
The mean difference in QALYs at 6 and 18 months and 95% CIs were calculated using regression analysis adjusting for baseline utility, with site as a covariate and bias-corrected bootstrapping with 1000 iterations for complete cases (complete CHU9D at baseline and at 3-, 6-, 12- and 18-month follow-ups).
We assumed data were missing at random. Predictors of missingness were explored, with site identified as the only predictor of missingness. In line with the statistical analysis of the primary outcome we have conducted a complete case analysis adjusting for predictors of missingness.
Incremental cost-effectiveness ratio
We explore the mean incremental cost per QALY gained and the mean cost per point reduction in YGTSS-TTSS comparing ERP and psychoeducation from the health and social care cost perspective at 18 months. Costs include total health-care resource use per participant and variable costs per participant for both trial arms. For the intervention arm, costs include the costs for the platform, therapist time, supervision and training. For the control arm, we do not include any platform or training and supervision costs, as we assume that the psychoeducation information could be provided without the need to use the platform (i.e. on a standalone website). However, therapist time is included given that this was provided as part of the active psychoeducation arm. The ICERs were calculated using seemingly unrelated regression (SUR; Stata command SUREG) to account for any potential correlation between costs and outcomes.
Cost-effectiveness acceptability planes and cost-effectiveness acceptability curves
The adjusted, bootstrapped SUR QALYs, TTSS and cost data were used to calculate the probability that ERP is cost-effective compared to psychoeducation for a range of cost-effectiveness threshold values. A cost-effectiveness plane of the bootstrapped results is also reported for both the YGTSS-TTSS and QALY analyses.
Sensitivity analyses
Sensitivity analyses were conducted to explore the impact of different assumptions regarding the cost of the intervention. Three assumptions were changed:
- Applying a licence fee per participant instead of a fixed cost per year based on a UK iCBT digital intervention.87 We apply different licence fees starting at £25 to explore how this impacts the probability of cost-effectiveness.
- Assuming fortnightly supervision instead of weekly supervision of therapists delivering the intervention.
- Adding the cost of the platform to the psychoeducation group to reflect how this might be rolled out in practice.
Secondary analysis: 10-year decision analytic model
A 10-year decision model allows us to project the costs incurred and health benefits accrued beyond the time horizon of the trial. Moreover, the decision model allows us to include an additional arm for CBIT, which is considered to be the ‘gold standard’ treatment for tics but is not currently widely available. Health service costs and QALYs were calculated for the 10 years following the trial, drawing on data from the trial and available literature where needed.
Design
In the model, cost-effectiveness is estimated by calculating which of three options – (1) online psychoeducation, (2) online ERP and (3) CBIT – has the highest net monetary benefit (NMB) for a range of QALY cost-effectiveness thresholds. The model was designed following a rapid review of the literature and informed by expert clinical input.
Cycle duration is 6 months, with 20 cycles in total to project the results forward 10 years to estimate how costs and outcomes might change for this patient group going into adulthood. The duration of 10 years was chosen to adequately capture long-term costs and QALYs, but such an analysis does not project so far into the future that the results might no longer hold. In line with NICE guidelines, costs and QALYs have been discounted at the recommended rate of 3.5% per year.80 There are associated costs and utility values for each of three health states of mild, moderate and severe tics.
Transition probabilities for ERP and psychoeducation were obtained during the trial follow-up between 6 and 18 months to measure the natural progression of tics following the intervention, as using data from baseline to 6 months would have overestimated the long-term impact by including the initial decrease in tic severity in the transition probabilities. Transition probabilities for CBIT were calculated from the literature (Markov model structure; Table 17). The mean utilities and costs associated with each health state were calculated using the patient-level data for the study.
| To very mild | To mild | To moderate | To severe | To very severe | |
|---|---|---|---|---|---|
| Online ERP and CBIT | |||||
| From very mild | 0.600 | 0.200 | 0.200 | 0.000 | 0.000 |
| From mild | 0.273 | 0.273 | 0.318 | 0.045 | 0.091 |
| From moderate | 0.023 | 0.279 | 0.535 | 0.070 | 0.093 |
| From severe | 0.000 | 0.000 | 0.214 | 0.786 | 0.000 |
| From very severe | 0.000 | 0.043 | 0.087 | 0.043 | 0.826 |
| Online psychoeducation | |||||
| From very mild | 0.250 | 0.750 | 0.000 | 0.000 | 0.000 |
| From mild | 0.143 | 0.643 | 0.071 | 0.071 | 0.071 |
| From moderate | 0.039 | 0.118 | 0.667 | 0.176 | 0.000 |
| From severe | 0.000 | 0.100 | 0.250 | 0.400 | 0.250 |
| From very severe | 0.000 | 0.000 | 0.043 | 0.217 | 0.739 |
The patient population in the model is assumed to be the same as that in the trial, including in terms of sample size and demographics.
The model was designed in Microsoft Excel® (Microsoft Corporation, Redmond, WA, USA), with inputs calculated in Stata version 17.81
Markov model structure
Following our rapid review of the literature, searching for tics/Tourette’s, young people/adolescents and economic evaluations, we were unable to identify any previous decision models for the treatment of tics in young people. Our review also identified that there is no official definition for what categorises mild to severe tics. We decided to base the model on the commonly referenced structure of severity suggested by Bloch and Leckman,88 where tics are categorised based on the TTSS on the YGTSS as very mild (0–9), mild (10–19), moderate (20–29), severe (30–39) or very severe (40–50). It is possible for individuals to go from any severity level to another each cycle within a relatively short period of time, although the probability of going from a very mild state to very severe and vice versa is close to zero (see Figure 6).
FIGURE 6 Markov model structure. (Figure not reproduced here; see the original article.)
Figure 7 shows tic progression over the course of the trial for online psychoeducation and ERP. Discussions with clinicians led us to conclude that it was feasible to simulate a decrease in tic severity in the CBIT group at 6 months from the trial literature data, shown by the dashed line in Figure 7, and then assume a similar tapering to ERP, shown in Figure 7 after 6 months. For this reason, the transition probabilities applied to the CBIT arm after 6 months are the same as those drawn from the trial for the ERP arm.
FIGURE 7 Tic progression over time by group. (Figure not reproduced here; see the original article.)
Figures 8 and 9 show the proportions of participants in each group that fell into each health state at baseline and at 6 months, respectively. These results illustrate patients moving into lower-severity health state and tic scores falling over time. Table 18 reports the proportions of participants in each group when they enter the model and begin moving through the health states using the transition probabilities reported in Table 17. For the probabilistic sensitivity analysis (PSA), transition probabilities were sampled using the Dirichlet distribution.89 Values for CBIT were obtained by combining data from the available literature on CBIT effectiveness for young people at 6 months.17,59,90,91
FIGURE 8 Proportions of participants in each tic severity health state by group at baseline. (Figure not reproduced here; see the original article.)
FIGURE 9 Proportions of participants in each tic severity health state by group at 6 months. (Figure not reproduced here; see the original article.)
| Online ERP(18 months) (%) | Online psychoeducation(18 months) (%) | Face-to-face CBIT(6 months) (%) | |
|---|---|---|---|
| Very mild | 12 | 4 | 10 |
| Mild | 19 | 18 | 38 |
| Moderate | 33 | 37 | 42 |
| Severe | 14 | 21 | 9 |
| Very severe | 22 | 21 | 1 |
Calculating health-care costs and utilities
Cost of online ERP
The mean cost per participant of ERP came from the trial results reported above. In the base case scenario this is the same as what is reported in the trial analysis: £155. This includes £104.57 for the online platform and supervision and a mean variable cost of £50.43 per participant for therapist time in the trial.
Cost of online psychoeducation
In the trial analysis the cost of the platform was not included for the psychoeducation arm as it was assumed in practice that this was unlikely to be delivered online. The cost of therapist support was included to reflect the additional support that these patients received compared to what would be available in usual care. This led to a mean cost per participant of £43.76, which is what was used as the base case in the model.
Cost of face-to-face CBIT
In the available literature, CBIT is consistently referred to as consisting of eight sessions, two lasting 90 minutes for the purpose of building rapport and six 60-minute sessions.59,91 This was confirmed by specialist tic clinics, which also provided information on who normally delivers CBIT in the UK. Based on this, CBIT was assumed to be delivered by a grade 8a clinical psychologist over the course of 9 hours, resulting in a cost per simulated participant of £675.
Health state costs
Health state costs associated with each level of tic severity included costs associated with the use of specialist tic services as these were the only costs collected as part of the trial that had a significant relationship with tic severity. The average cost per participant at each severity level was calculated adjusting for age, comorbidities using the DAWBA and sex.
Costs for patients in the online psychoeducation arm and online ERP between 0 and 18 months were calculated using information on tic severity available in the trial. These patients then enter the model at 18 months. Those in the CBIT arm effectively enter the model at 6 months based on their level of tic severity after the simulated decrease between baseline and 6 months.
Health state utilities
The relationship between tic severity and HRQoL is not clear. Some studies have found a positive relationship between tic severity and factors relating to QoL, such as functional impairment and psychosocial scores in children.92,93 A few studies have found that tic severity only has a small impact on HRQoL, if any, and that a greater contributor is comorbidities. Some studies have found a significant relationship between tic severity and HRQoL.94–97 We therefore included key significant comorbidities using the DAWBA data from the trial as well as age and sex when calculating CHU9D utility values for tic health states.
Analysis of the trial data showed that transitioning from one of the mild-severity health states to a moderate-severity health state had a significant impact on costs and utility values, but there was no statistically significant difference between a very-mild-severity and a mild-severity health state. Similarly, there was a significant difference in costs and utilities between a moderate-severity health state and the severe health states, but there was no difference between severe and very severe tics. Therefore, costs and utilities are allocated as illustrated by Figure 10. Means, standard errors and distributions calculated from the trial data for use in the model are reported in Table 19. Utilities were divided by two when applied to health states to reflect the 6-month cycle duration.
FIGURE 10 Allocation of costs and utilities according to health states. (Figure not reproduced here; see the original article.)
| Value | SE | Distribution | |
|---|---|---|---|
| 6-month health-care costs | |||
| Mild | £129 | 15.21 | Gamma |
| Moderate | £133 | 12.63 | Gamma |
| Severe | £194 | 19.02 | Gamma |
| Utility weights on CHU9D | |||
| Utility | SE | Distribution | |
| Mild | 0.867 | 0.006 | Beta |
| Moderate | 0.839 | 0.004 | Beta |
| Severe | 0.814 | 0.005 | Beta |
Cost-effectiveness analysis
We calculated the total costs and QALYs for patients treated with online ERP compared with online psychoeducation and face-to-face CBIT. We calculated an individual ICER for ERP compared with psychoeducation and ERP compared with CBIT. We also calculated the NMB of each intervention to be able to more easily compare all three options. Any costs and QALYs obtained after 12 months were discounted at 3.5% in line with NICE guidance.80
Sensitivity analysis
Deterministic analysis and PSA were used to explore the uncertainty regarding our results.
Deterministic analysis
We varied the input variables, either in combination or alone, while other inputs were held at a constant value. We used this to explore how changing assumptions regarding the cost components of the different interventions may impact the results. We implemented:
- a licence fee for the platform of £25 per participant based on the sensitivity analysis we conducted for the main trial analysis
- including the cost of the platform for the online psychoeducation arm to reflect how much it would cost to roll out this intervention in this manner
- setting the cost of online psychoeducation to £0 to provide a conservative estimate of how cost-effective online ERP would be compared with a ‘do nothing’ approach
- applying the same transition probabilities to the online psychoeducation arm as were applied to the online ERP and CBIT arms.
Probabilistic sensitivity analysis and cost-effectiveness acceptability curve
We computed 5000 replications of the model in our PSA, varying the values as set out in Tables 17 and 19. The 5000 replications were then used to construct cost-effectiveness acceptability curves (CEACs) showing the probability that online ERP was cost-effective compared with online psychoeducation and face-to-face CBIT for a range of cost-effectiveness threshold values using the NMB approach, where NMB equals total QALYs multiplied by a cost-effectiveness threshold minus total costs.
Results
Costs of the intervention
The fixed and variable costs of the BIP platform and therapist support are reported in Tables 20–23. For variable login costs, the mean cost per patient was £1.25 higher (95% CI £0.46 to £2.04) for the intervention arm compared to the control. For variable therapist support costs, the mean cost per patient was £5.03 higher (95% CI £0.88 to £9.97) for ERP compared to psychoeducation.
| Item | Data |
|---|---|
| Cost per year in SEK | 96,000 |
| Cost per year in GBP September 2020 | 8494 |
| N of participants in online ERP arm using platform | 111 |
| Fixed cost of platform per participant in GBP | 77 |
| ERP therapy | Psychoeducation | |||
|---|---|---|---|---|
| Mean (£) | SD (£) | Mean (£) | SD (£) | |
| Child | 3.36 | 1.85 | 2.54 | 1.46 |
| Parent 1 | 3.46 | 1.95 | 3.07 | 1.52 |
| Parent 2 | 0.04 | 0.33 | 0.01 | 0.10 |
| Total | 6.87 | 3.54 | 5.62 | 2.62 |
| Item | Description | Grade | Total costs (£) |
|---|---|---|---|
| Independent training | Total of 10 hours of independent time reported | 1 grade 4 research assistant1 grade 5 nurse | 177 |
| Therapist time to attend supervision | Weekly supervision lasting 1 hour over 108 weeks | 1 grade 4 research assistant3 grade 5 nurses | 7825 |
| Delivery of supervision | Weekly supervision lasting 1 hour over the 108 weeks | 1 grade 8c clinician1 grade 7 nurse practitioner | 6894 |
| ERP therapy | Psychoeducation | |||
|---|---|---|---|---|
| Mean (£) | SD (£) | Mean (£) | SD (£) | |
| Therapist time | ||||
| Child | 18 | 9 | 16 | 9 |
| Parent 1 | 25 | 13 | 22 | 10 |
| Parent 2 | 0.29 | 2 | 0.09 | 1 |
| Total | 43 | 20 | 38 | 17 |
| Phone cost | ||||
| Child | 0.01 | 0.14 | 0 | 0.02 |
| Parents | 0.29 | 1 | 0.27 | 1 |
| Parent and child | 0.02 | 0.16 | 0.02 | 0.16 |
| Total | 0.33 | 1 | 0.29 | 1 |
| Total therapist cost | 43 | 20 | 38 | 17 |
Primary analysis: analysis alongside the RCT
Resource use and costs
Table 24 reports the mean number of contacts and SDs for the reported numbers and percentages who have used the specialist tic service. Other service uses and medication uses are reported in Tables 25 and 26. There was no significant difference in costs between the two groups, with means per-patient differences in total resource use cost (excluding intervention costs) at 6 months of £63 (95% CI −£158 to £284) and £192.79 (95% CI −£251.74 to £637.32) at 18 months for the intervention arm compared with the control (see Table 27). School-related information is reported in the separate health economic analysis document.
| ERP therapy | Psychoeducation | |||
|---|---|---|---|---|
| N (%) | Meana (SD) | N (%) | Meana (SD) | |
| Specialist tic clinic | ||||
| Baseline | 9 (8%) | 1 (0) | 5 (4%) | 1 (0) |
| 3 months | 6 (6%) | 1 (1) | 3 (3%) | 2 (1) |
| 6 months | 0 (0%) | 0 (0) | 6 (6%) | 2 (1) |
| 12 months | 6 (7%) | 3 (2) | 6 (7%) | 3 (3) |
| 18 months | 7 (8%) | 1 (0) | 8 (9%) | 1 (0) |
| CAMHS | ||||
| Baseline | 34 (30%) | 3 (3) | 28 (25%) | 2 (2) |
| 3 months | 19 (19%) | 3 (3) | 24 (24%) | 2 (2) |
| 6 months | 20 (22%) | 3 (4) | 25 (27%) | 3 (3) |
| 12 months | 22 (24%) | 3 (2) | 28 (31%) | 4 (6) |
| 18 months | 21 (24%) | 3 (3) | 26 (29%) | 4 (6) |
| Paediatrician in hospital | ||||
| Baseline | 18 (16%) | 1 (1) | 15 (13%) | 1 (0) |
| 3 months | 9 (9%) | 1 (0) | 9 (9%) | 1 (0) |
| 6 months | 12 (13%) | 1 (0) | 8 (9%) | 1 (0) |
| 12 months | 10 (11%) | 1 (1) | 8 (9%) | 2 (1) |
| 18 months | 7 (8%) | 1 (1) | 10 (11%) | 1 (0) |
| Paediatrician in the community | ||||
| Baseline | 5 (4%) | 1 (0) | 5 (4%) | 1 (0) |
| 3 months | 5 (5%) | 1 (0) | 3 (3%) | 1 (0) |
| 6 months | 2 (2%) | 2 (1) | 2 (2%) | 1 (0) |
| 12 months | 1 (1%) | 2 (0) | 0 (0%) | 0 (0) |
| 18 months | 2 (2%) | 1 (0) | 1 (1%) | 1 (0) |
| Child and adolescent psychiatrist | ||||
| Baseline | 2 (2%) | 2 (1) | 4 (4%) | 2 (1) |
| 3 months | 2 (2%) | 2 (1) | 4 (4%) | 3 (4) |
| 6 months | 2 (2%) | 4 (2) | 4 (4%) | 1 (1) |
| 12 months | 1 (1%) | 2 (0) | 4 (4%) | 1 (0) |
| 18 months | 2 (2%) | 1 (0) | 0 (0%) | 0 (0) |
| Neurologist | ||||
| Baseline | 2 (2%) | 1 (0) | 4 (4%) | 1 (0) |
| 3 months | 0 (0%) | 0 (0) | 3 (3%) | 1 (0) |
| 6 months | 6 (6%) | 3 (4) | 3 (3%) | 1 (0) |
| 12 months | 5 (6%) | 1 (0) | 4 (4%) | 1 (1) |
| 18 months | 4 (4%) | 2 (1) | 1 (1%) | 1 (0) |
| Child and adolescent psychologist | ||||
| Baseline | 1 (1%) | 2 (0) | 2 (2%) | 6 (6) |
| 3 months | 2 (2%) | 0 (0) | 2 (2%) | 1 (0) |
| 6 months | 2 (2%) | 2 (1) | 2 (2%) | 2 (1) |
| 12 months | 2 (2%) | 6 (1) | 3 (3%) | 2 (1) |
| 18 months | 0 (0%) | 0 (0) | 2 (2%) | 2 (1) |
| Speech and language therapist | ||||
| Baseline | 3 (3%) | 1 (1) | 2 (2%) | 1 (0) |
| 3 months | 6 (6%) | 2 (1) | 2 (2%) | 7 (7) |
| 6 months | 3 (3%) | 6 (5) | 0 (0%) | 0 (0) |
| 12 months | 4 (4%) | 4 (4) | 1 (1%) | 20 (0) |
| 18 months | 1 (1%) | 20 (0) | 0 (0%) | 0 (0) |
| Occupational therapist | ||||
| Baseline | 2 (2%) | 1 (0) | 2 (2%) | 3 (2) |
| 3 months | 4 (4%) | 1 (0) | 3 (3%) | 1 (0) |
| 6 months | 4 (4%) | 7 (9) | 0 (0%) | 0 (0) |
| 12 months | 5 (6%) | 4 (4) | 2 (2%) | 11 (13) |
| 18 months | 3 (3%) | 7 (11) | 1 (1%) | 2 (0) |
| ERP therapy | Psychoeducation | |||
|---|---|---|---|---|
| N (%) | Meana (SD) | N (%) | Meana (SD) | |
| Other primary care contacts | ||||
| Baseline | 75 (67%) | 4 (6) | 69 (62%) | 6 (9) |
| 3 months | 58 (57%) | 3 (5) | 58 (58%) | 3 (3) |
| 6 months | 46 (49%) | 4 (5) | 61 (66%) | 3 (4) |
| 12 months | 46 (53%) | 4 (8) | 52 (58%) | 4 (5) |
| 18 months | 46 (53%) | 6 (16) | 52 (58%) | 3 (3) |
| Accident and emergency contacts | ||||
| Baseline | 6 (5%) | 1 (0) | 11 (10%) | 1 (0) |
| 3 months | 2 (2%) | 1 (0) | 7 (7%) | 1 (1) |
| 6 months | 5 (5%) | 2 (1) | 5 (5%) | 1 (0) |
| 12 months | 10 (11%) | 1 (0) | 12 (13%) | 2 (2) |
| 18 months | 7 (8%) | 1 (0) | 7 (8%) | 1 (0) |
| Other secondary care contacts | ||||
| Baseline | 3 (3%) | 1 (1) | 1 (1%) | 1 (0) |
| 3 months | 1 (1%) | 5 (0) | 1 (1%) | 1 (0) |
| 6 months | 0 (0%) | 0 (0) | 1 (1%) | 1 (0) |
| 12 months | 0 (0%) | 0 (0) | 0 (0%) | 0 (0) |
| 18 months | 3 (3%) | 9 (10) | 1 (1%) | 1 (0) |
| ERP therapy | Psychoeducation | |
|---|---|---|
| N (%) | N (%) | |
| Clonidine | ||
| Baseline | 4 (4%) | 9 (8%) |
| 3 months | 3 (3%) | 10 (10%) |
| 6 months | 4 (4%) | 7 (8%) |
| 12 months | 3 (3%) | 6 (7%) |
| 18 months | 1 (1%) | 5 (6%) |
| Risperidone | ||
| Baseline | 0 (0%) | 3 (3%) |
| 3 months | 0 (0%) | 2 (2%) |
| 6 months | 0 (0%) | 1 (1%) |
| 12 months | 1 (1%) | 2 (2%) |
| 18 months | 2 (2%) | 3 (3%) |
| Aripiprazole | ||
| Baseline | 7 (6%) | 1 (1%) |
| 3 months | 5 (5%) | 1 (1%) |
| 6 months | 5 (5%) | 0 (0%) |
| 12 months | 6 (7%) | 1 (1%) |
| 18 months | 4 (5%) | 2 (2%) |
| Any tic medication a | ||
| Baseline | 14 (13%) | 16 (14%) |
| 3 months | 12 (12%) | 15 (15%) |
| 6 months | 15 (16%) | 8 (9%) |
| 12 months | 15 (18%) | 11 (12%) |
| 18 months | 11 (12%) | 12 (13%) |
| ERP therapy | Psychoeducation | Adjusted differencea(95% CI) | p-value | |
|---|---|---|---|---|
| Mean (SD) | Mean (SD) | |||
| Specialist tic services | ||||
| Baseline | 128 (248) | 91 (168) | ||
| 3 months | 158 (314) | 121 (242) | ||
| 6 months | 200 (384) | 192 (414) | ||
| 12 months | 149 (271) | 209 (506) | ||
| 18 months | 145 (305) | 102 (192) | ||
| 18 months discounted | 140 (295) | 99 (186) | ||
| Total | 719 (988) | 643 (1046) | −3.28 (−284.66 to 278.1) | 0.982 |
| Community services | ||||
| Baseline | 73 (166) | 82 (178) | ||
| 3 months | 68 (149) | 55 (104) | ||
| 6 months | 94 (277) | 93 (183) | ||
| 12 months | 66 (213) | 95 (164) | ||
| 18 months | 159 (657) | 83 (131) | ||
| 18 months discounted | 153 (635) | 80 (127) | ||
| Total | 478 (1259) | 381 (432) | 91.04 (−131.43 to 313.52) | 0.423 |
| Hospital services | ||||
| Baseline | 10 (107) | 14 (147) | ||
| 3 months | 28 (282) | 9 (87) | ||
| 6 months | 0 (0) | 6 (59) | ||
| 12 months | 0 (0) | 0 (0) | ||
| 18 months | 99 (529) | 32 (305) | ||
| 18 months discounted | 96 (511) | 31 (295) | ||
| Total | 141 (658) | 58 (347) | 90.58 (−46.8 to 227.96) | 0.196 |
| Accident and emergency | ||||
| Baseline | 8 (41) | 21 (77) | ||
| 3 months | 6 (37) | 24 (92) | ||
| 6 months | 19 (89) | 14 (63) | ||
| 12 months | 0 (0) | 0 (0) | ||
| 18 months | 19 (68) | 14 (49) | ||
| 18 months discounted | 18 (66) | 14 (48) | ||
| Total | 43 (113) | 78 (185) | −15.18 (−52.42 to 22.05) | 0.424 |
| Medication costs | ||||
| Baseline | 13 (31) | 13 (32) | ||
| 6 months | 15 (44) | 9 (30) | ||
| 12 months | 64 (146) | 50 (122) | ||
| 18 months | 69 (145) | 44 (130) | ||
| 18 months discounted | 66 (140) | 42 (125) | ||
| Total | 168 (309) | 134 (291) | 48.17 (−21.8 to 118.15) | 0.177 |
| Total healthcare resource use costs | ||||
| Baseline | 231 (361) | 221 (333) | ||
| 3 months | 280 (542) | 227 (342) | ||
| 6 months | 328 (565) | 314 (502) | ||
| 12 months | 279 (475) | 354 (575) | ||
| 18 months | 491 (1104) | 275 (446) | ||
| 18 months discounted | 474 (1067) | 266 (431) | ||
| Total health-care costs | 1549 (2340) | 1294 (1434) | 192.79 (−251.74 to 637.32) | 0.395 |
There were no significant differences in total wider costs (excluding intervention costs) at 6 months (mean difference of £117.07 per participant, 95% CI −£205.95 to £440.09) and 18 months (mean difference of £302.73 per participant, 95% CI −£327.26 to £932.72). The mean differences in costs also were not significant when total health-care costs were added to the wider societal costs [£203.16 (95% CI −£241.03 to £647.34) at 6 months and £576.77 (95% CI −£413.55 to £1567.10) at 18 months].
Utilities and QALYs
The follow-up rate for the CHU9D was lower than for the CA-SUS, as this was collected separately online from the other questionnaires. At 6 months, QALYs for the young-person self-completed CHU9D were 0.011 (95% CI 0.000 to 0.022) higher for those in the ERP group compared to those in the psychoeducation group (see Table 28). There were no statistically significant differences between arms for the parent proxy-completed CHU9D at 6 months (0.007, 95% CI −0.002 to 0.017) or at 18 months for the young-person (0.036, 95% CI −0.015 to 0.087) or proxy parent/carer (0.036, 95% CI −0.006 to 0.008) CHU9D.
| ERP therapy | Psychoeducation | Adjusted differencea (95% CI) | p-value | |||||
|---|---|---|---|---|---|---|---|---|
| N | Mean | SD | N | Mean | SD | |||
| Parent-completed | ||||||||
| Baseline | 112 | 0.832 | 0.085 | 112 | 0.845 | 0.088 | ||
| 3 months | 89 | 0.853 | 0.091 | 92 | 0.822 | 0.107 | ||
| 6 months | 64 | 0.849 | 0.106 | 76 | 0.841 | 0.110 | ||
| 12 months | 66 | 0.857 | 0.124 | 65 | 0.816 | 0.115 | ||
| 18 months | 52 | 0.838 | 0.117 | 54 | 0.834 | 0.113 | ||
| 18 months discounted | 52 | 0.810 | 0.113 | 54 | 0.806 | 0.109 | ||
| QALYs at 6 months | 63 | 0.425 | 0.039 | 74 | 0.417 | 0.040 | 0.007 (−0.002 to 0.017) | 0.140 |
| QALYs at 12 months | 52 | 0.858 | 0.087 | 54 | 0.834 | 0.083 | ||
| QALYs at 18 months | 46 | 1.285 | 0.126 | 41 | 1.246 | 0.118 | 0.036 (−0.006 to 0.077) | 0.094 |
| Young person-completed | ||||||||
| Baseline | 112 | 0.815 | 0.097 | 112 | 0.827 | 0.094 | ||
| 3 months | 86 | 0.866 | 0.102 | 89 | 0.831 | 0.117 | ||
| 6 months | 63 | 0.853 | 0.118 | 66 | 0.814 | 0.122 | ||
| 12 months | 60 | 0.856 | 0.102 | 61 | 0.810 | 0.127 | ||
| 18 months | 45 | 0.840 | 0.100 | 49 | 0.811 | 0.133 | ||
| 18 months discounted | 45 | 0.812 | 0.096 | 49 | 0.784 | 0.129 | ||
| QALYs at 6 months | 59 | 0.425 | 0.049 | 65 | 0.418 | 0.043 | 0.011 (0.000 to 0.022) | 0.048a |
| QALYs at 12 months | 47 | 0.842 | 0.103 | 46 | 0.825 | 0.092 | ||
| QALYs at 18 months | 38 | 1.264 | 0.132 | 33 | 1.236 | 0.134 | 0.036 (−0.015 to 0.087) | 0.169 |
Primary analysis: mean incremental cost per QALY gained of ERP compared to psychoeducation at 18 months based on proxy parent/carer responses to the CHU9D
From a health and social care cost perspective at 18 months, accounting for the correlation between costs and QALYs using SUR and adjusting for baseline utility and site, the mean incremental cost per participant of ERP compared to psychoeducation was £662 (95% CI −£59 to £1384), with a mean incremental QALY calculated using the parent-completed CHU9D of 0.040 (95% CI −0.004 to 0.083) per participant and an incremental cost per QALY gained of £16,708. The cost-effectiveness acceptability plane (CEAP) is shown in Figure 11. At a cost-effectiveness threshold of £20,000 per QALY there is a 65% probability that ERP is cost-effective, increasing to 79% at a threshold value of £30,000 per QALY (see Figure 12).
FIGURE 11 Cost-effectiveness acceptability plane QALY analysis using parent-completed CHU9D. Note: Figure in Hollis et al.79 (Figure not reproduced here; see the original article.)
FIGURE 12 Cost-effectiveness acceptability curve QALY analysis using parent-completed CHU9D. Note: Figure in Hollis et al.79 (Figure not reproduced here; see the original article.)
From a wider cost perspective, the mean incremental cost per participant of ERP compared to psychoeducation was £1080 (95% CI −£351 to £2510), with a mean incremental QALY calculated using the parent-completed CHU9D of 0.035 (95% CI −0.004 to 0.083) per participant and an incremental cost per QALY gained of £16,708. The incremental cost per QALY gained was £30,480, with a 53% probability of being cost-effective compared with the control at a cost-effectiveness threshold of £30,000 per QALY.
Figure 13 reports the CEAP using incremental QALYs calculated from young person self-completed CHU9D responses. The mean incremental cost per participant of ERP compared to psychoeducation was £156 (95% CI −£637 to £950), with a mean incremental QALY calculated using the young person-completed CHU9D of 0.038 (95% CI −0.015 to 0.090) per participant and an incremental cost per QALY gained of £4139. At a cost-effectiveness threshold of £20,000 the ERP intervention has an 84% probability of being cost-effective, increasing to 88% at a threshold of £30,000 per QALY gained. The CEAC for this analysis is reported in Figure 14.
FIGURE 13 Cost-effectiveness acceptability plane QALY analysis using young person-completed CHU9D. Note: Secondary analysis: mean incremental cost per QALY gained of ERP compared to psychoeducation at 18 months is based on young person self-completed responses to the CHU9D. (Figure not reproduced here; see the original article.)
FIGURE 14 Cost-effectiveness acceptability curve QALY analysis using young person-completed CHU9D. Note: Secondary analysis: probability that ERP is cost-effective compared to psychoeducation at 18 months is based on young person self-completed responses to the CHU9D. (Figure not reproduced here; see the original article.)
From a wider cost perspective, the incremental cost per QALY gained at 18 months is £10,053 (mean incremental cost of £381, 95% CI −£950 to £1713). The probability of the ERP intervention being cost-effective compared to psychoeducation from a wider cost perspective at a threshold of £20,000 per QALY gained is 69%, and it is 79% at £30,000 per QALY gained.
At 18 months, the incremental mean cost per patient of ERP compared with psychoeducation, including intervention costs, was £305 (95% CI −£136 to £746), with a mean reduction of −1.68 points on the YGTSS-TTSS (95% CI −3.79 to −0.43) and an incremental cost per reduction in YGTSS-TTSS (YGTSS-TTSS multiplied by −1) of £182 from a health and social care cost perspective. The ICER is reported in the CEAP in Figure 15. There is a 90% probability that ERP is cost-effective compared with psychoeducation for cost-effectiveness thresholds > £1000 per point reduction in YGTSS-TTSS (see Figure 16).
FIGURE 15 Cost-effectiveness acceptability plane for TTSS analysis. Note: Figure in Hollis et al.79 (Figure not reproduced here; see the original article.)
FIGURE 16 Cost-effectiveness acceptability curve for a cost per point reduction on the TTSS. Note: Secondary analysis: mean incremental cost per unit change on the TTSS of ERP compared to psychoeducation at 18 months. Figure in Hollis et al.79 (Figure not reproduced here; see the original article.)
From a wider cost perspective, the incremental cost per point reduction in YGTSS-TTSS was £346.3, with an 86% probability of being cost-effective compared with the control at a cost-effectiveness threshold of £1000 per point reduction in YGTSS-TTSS. (Please note the ICER has not been multiplied by −1 so the interpretation of the plane is reversed.)
Sensitivity analysis
In order to explore how different costing models for the platform impact the cost-effectiveness of the intervention we applied a licence fee starting at £25 per participant and increasing by £10 increments up to £165. Figure 17 shows that at a licence fee of £25 per participant ERP has an 82% chance of being cost-effective at a threshold value of £30,000 per QALY gained; this falls to 77% when the licence fee was set to £165 per participant. This small range would suggest that at a threshold value of £30,000 per QALY gained there is little uncertainty around ERP being cost-effective compared with psychoeducation, even if the cost of rolling out the intervention was marginally more expensive than expected from the trial.
FIGURE 17 Impact of different licence fees on probability of cost-effectiveness at a threshold of £30,000 per QALY gained. Note: Figure in Hollis et al.79 (Figure not reproduced here; see the original article.)
We see similar results at a threshold value of £1000 per point reduction in YGTSS-TTSS. As there is no official threshold for a point reduction in YGTSS-TTSS we also conducted this for a threshold value of £200 per point reduction in YGTSS-TTSS and found that the probability of cost-effectiveness falls below 50% at a licence fee per participant of £155 or more.
As therapists were trained during supervision, it is feasible to assume that once fully trained and familiar with the delivery of the intervention only fortnightly supervision would be necessary. When applying fortnightly supervision, the fixed cost of the intervention falls from £104 to £71. This results in an ICER of £162 per point reduction in YGTSS-TTSS and a probability of 90% of being cost-effective compared with psychoeducation at a threshold of £1000 per point reduction in YGTSS-TTSS.
Using the parent-completed CHU9D, when supervision is assumed to be fortnightly this results in an ICER of £15,885 per QALY gained, and there is an 81% probability that ERP is cost-effective compared with psychoeducation at a threshold of £30,000 per QALY gained.
Given psychoeducation was also delivered through the platform and the possibility of trying to provide this as an alternative intervention side by side with ERP but without the requirement of therapist support, an alternative sensitivity analysis added the fixed platform cost to the psychoeducation arm. This increased the probability of cost-effectiveness to 71% using parent-completed CHU9D at a threshold value of £20,000 per QALY gained and 83% at a threshold value of £30,000 per QALY gained.
Secondary analysis: 10-year decision analytic model
We report the mean total cost and QALYs accrued per participant over the course of the 10 years in the model for each intervention. After 5000 replications, online ERP cost an additional £70.76 per participant compared with psychoeducation and resulted in an additional 0.009 QALYs per participant. This resulted in an ICER of £8276 per QALY gained. CBIT cost an additional £537.38 per participant compared to online ERP and led to an additional 0.018 QALYs per participant.
Figure 18 shows the probability that each intervention is cost-effective at different cost-effectiveness threshold values. At cost-effectiveness thresholds below than £10,000 per QALY gained, psychoeducation has the highest probability of being cost-effective. ERP is cost-effective compared with CBIT at cost-effectiveness threshold values below £30,000 per QALY gained. Figure 19 shows the CEAC for ERP compared with CBIT alone; there is a > 94% chance that ERP is cost-effective compared with CBIT at threshold values of £20,000 per QALY gained or below.
FIGURE 18 Cost-effectiveness acceptability curve showing the probability each intervention is cost-effective at a range of threshold values. (Figure not reproduced here; see the original article.)
FIGURE 19 Cost-effectiveness acceptability curve showing the probability that ERP is cost-effective compared with CBIT. (Figure not reproduced here; see the original article.)
Figure 20 shows that there is a > 50% chance that online ERP is cost-effective compared with psychoeducation from threshold values of £10,000 per QALY gained or more.
FIGURE 20 Cost-effectiveness acceptability curve showing the probability that online ERP is cost-effective compared with online psychoeducation. (Figure not reproduced here; see the original article.)
Sensitivity analysis
When the platform was assumed to work on a licence fee basis, online ERP was cost-effective compared with online psychoeducation from threshold values of £4000 per QALY gained. This analysis had little impact on the probability of being cost-effective compared with CBIT; online ERP became cost-effective up to values of £31,000 per QALY gained.
When the cost of psychoeducation was assumed to include the platform cost, online ERP is cost-effective compared with psychoeducation from threshold values of £5000 per QALY gained.
In a sensitivity analysis in which we applied a cost of £0 to online psychoeducation, online ERP was cost-effective from threshold values of £13,000 per QALY gained or more.
Applying the same transition probabilities to all of the groups also lowered the threshold at which online ERP is cost-effective compared with online psychoeducation to £3000 per QALY gained.
Conclusion
The 18-month time horizon is long enough to be able to conduct a full economic evaluation and we found that ERP has a 79% chance of being cost-effective compared with psychoeducation at a cost-effectiveness threshold of £30,000 per QALY gained. This is likely to be conservative given that psychoeducation is already better than what is widely available as treatment as usual. Moreover, the cost of the platform is not included for this group in the trial analysis as it was assumed that this information would normally be available elsewhere. When this cost is included the probability of cost-effectiveness goes up to 83%.
Most of the sensitivity analyses conducted have little impact on the results, suggesting that we can be reasonably confident that these results accurately reflect the cost-effectiveness of ERP compared with psychoeducation at 18 months. The initial naturalistic follow-up suggests that benefits of the intervention can be maintained past the initial intervention.
There was a higher probability that the intervention was cost-effective when the young person self-completed responses to the CHU9D are used to calculate QALYs, with a significant difference in QALYs in favour of ERP at 6 months. We pre-specified in the HEAP that the proxy parent/carer-completed CHU9D would be used to calculate QALYs in the primary analysis. This was due to the assumption that we might have a larger number of young people who might not compete the CHU9D, as did indeed happen. Further work is required to determine the suitability of proxy parent/carer-reported CHU9D for tics. Our work on determining health states for the model demonstrated that there was a significant difference in CHU9D proxy utility scores between mild, moderate and severe YGTSS-TTSS, suggesting that the changes in the CHU9D do correspond to the key clinical mechanism of interest in this trial: reducing tics.
The results of the long-term decision model suggest that online ERP is more than 50% cost-effective compared with the active control of online psychoeducation at threshold values considered acceptable by NICE. When we account for the cost of the platform in the online psychoeducation arm, online ERP becomes cost-effective at threshold values of £5000 per QALY gained, suggesting that if the NICE threshold is higher than this for a QALY gained it is more cost-effective to roll out online ERP than online psychoeducation using a similar platform. Even under the assumption that the cost of the active control is £0, which will be underestimating the cost-effectiveness given that it is still accounting for the benefit of online psychoeducation without the cost, online ERP is over 50% cost-effective from threshold values of £13,000 per QALY gained.
Online ERP has a > 50% chance of being cost-effective compared with CBIT at threshold values below £30,000 per QALY gained and a > 94% probability of cost-effectiveness at threshold values of £20,000 per QALY gained or below. Given research showing that the opportunity cost is likely to be closer to £13,000 than £30,000 per QALY gained, the more cost-effective intervention appears to be online ERP.98 Moreover, even in a situation in which we were able to pay £30,000 per QALY gained for CBIT, this would not resolve the lack of therapists available in the UK to deliver this intervention. The results of the decision model suggest that the remotely delivered ERP intervention can provide an alternative to face-to-face CBIT therapy, with only minimal impact on HRQoL.