Estimation of utilities in attention-deficit hyperactivity disorder for economic evaluations

A systematic review of health state utility values and psychometric performance of generic preference-based instruments for children and adolescents with mental health problems

AIMS

This paper aims to systematically identify reported health state utility values (HSUVs) in children and adolescents with mental health problems (MHPs) aged less than 25 years; to summarise the techniques used to elicit HSUVs; and to examine the psychometric performance of the identified multi-attribute utility instruments (MAUIs) used in this space.

METHODS

A systematic review was conducted following PRISMA guidelines. Peer-reviewed studies published in English, reporting HSUVs for children and adolescents with MHPs using direct or indirect valuation methods were searched in six databases.

RESULTS

We found 38 studies reporting HSUVs for 12 types of MHPs across 12 countries between 2005 and October 2021. Attention deficit hyperactivity disorder (ADHD) and depression are the most explored MHPs. Disruptive Behaviour Disorder was associated with the lowest reported HSUVs of 0.06 while cannabis use disorder was associated with the highest HSUVs of 0.88. Indirect valuation method through the use of MAUIs (95% of included studies) was the most frequently used approach, while direct valuation methods (Standard Gamble, Time Trade-Off) were only used to derive HSUVs in ADHD. This review found limited evidence of the psychometric performance of MAUIs used in children and adolescents with MHPs.

CONCLUSION

This review provides an overview of HSUVs of various MHPs, the current practice to generate HSUVs, and the psychometric performance of MAUIs used in children and adolescents with MHPs. It highlights the need for more rigorous and extensive psychometric assessments to produce evidence on the suitability of MAUIs used in this area.

Cost-Effectiveness and Cost Utility of Treatment of Attention-Deficit/Hyperactivity Disorder: A Systematic Review

Objectives: This systematic review provides an overview of full economic evaluations of attention-deficit/hyperactivity disorder (ADHD) treatments, evaluates their outcomes, and highlights gaps in the literature. Data Sources: Electronic databases were searched for full economic evaluations of ADHD treatments for children, adolescents, or adults published in English or Dutch. Results: Twenty-nine studies met the inclusion criteria. Almost all studies that compared medication or psychosocial treatment to no treatment, placebo, or care as usual indicated that medication and psychosocial treatment were cost-effective compared to the control group. Stimulant treatment appeared to be cost-effective for the treatment of ADHD in children and adolescents. Only few studies focus on treatments in adults and psychosocial treatments and the number of studies with long time horizons and without industry funding is limited. Conclusions: Despite the rising interest in cost-effectiveness, this systematic review shows that more cost-effectiveness research of higher quality is warranted to aid in the optimal use of available treatments and resources for individuals with ADHD. Specifically, more studies should focus on treatments in adults and psychosocial treatments, and more studies with long time horizons and without industry funding are warranted. Nevertheless, we can conclude that treating ADHD is generally cost-effective compared to no treatment. PROSPERO: CRD42017060074. Available from: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=60074.

Quantifying the Burden of Hyperphagia in Prader-Willi Syndrome Using Quality-Adjusted Life-years

BACKGROUND

Prader-Willi syndrome (PWS) is a rare disease associated with cognitive impairment, hypotonia, hyperphagia (an insatiable hunger), and obesity. Therapies that target hyperphagia are in development, but understanding the value of these therapies to inform patient-focused drug development (PFDD) requires valid data on disease burden. We estimated disease burden by measuring and comparing quality-adjusted life-years (QALYs) for 3 PWS health states relevant to current PFDD initiatives.

METHODS

Time trade-off (TTO) and a visual analog scale (VAS) were used to elicit PWS caregivers' values for 3 fixed health states for a standardized patient described with (1) untreated PWS, (2) PWS with controlled obesity, and (3) PWS with controlled obesity and hyperphagia. We excluded participants who left at least 1 TTO or VAS question blank or incomplete (noncompleters) and respondents who reported the same answer for all TTO scenarios (nontraders). The remaining group of respondents (traders) were used for all primary analyses. We assessed validity and bias of QALY estimates by comparing differences in health state valuations, treatment priorities, and characteristics among respondents who did and did not complete the TTO.

RESULTS

A total of 458 respondents completed the survey, including 226 traders, 93 nontraders, and 139 noncompleters. Traders valued untreated PWS at 0.69 QALYs, PWS with controlled obesity at 0.79 QALYs, and controlled hyperphagia/obesity at 0.91 QALY (P < 0.01 for differences among health state values). Reported VAS ratings were similar for traders versus nontraders for untreated PWS (38.64 vs 38.95, P = 0.89) and PWS with controlled obesity (57.36 vs 55.14, P = 0.35) but varied for PWS with controlled obesity and hyperphagia (70.70 vs 64.46, P = 0.02). Exclusion of noncompleters did not introduce obvious bias because traders and noncompleters were similar in treatment priorities and characteristics. The exclusion of nontraders did not meaningfully alter mean or distribution of valuations.

CONCLUSIONS

This study found that avoiding hyperphagia decreases the burden of PWS and that these results are robust, even once imposing strict inclusion criteria. Use of fixed health states to estimate QALYs addresses many of the complexities of measuring disease burden in rare and pediatric conditions, indicating the potential value of this approach to inform premarket decision makers in identifying outcome importance. (Clin Ther. 2021;XX:XXX-XXX) © 2021 Elsevier HS Journals, Inc.

Individual Variability in Reaction Time and Prediction of Clinical Response to Methylphenidate in Adult ADHD: A Prospective Open Label Study Using Conners' Continuous Performance Test II

Objective: The aim of this study was to examine whether reaction time parameters in adult patients with ADHD could predict their response to methylphenidate (MPH). Method: Previously unmedicated patients (N = 123) were administered the Conners' Continuous Performance Test II (CPT II) at baseline and after 6 weeks of treatment with immediate-release MPH. In addition to traditional CPT measures, we extracted intraindividual raw data and analyzed time series using linear and nonlinear mathematical models. Results: Clinical responders, assessed with the Clinical Global Impression-Improvement scale, showed significant normalization of target failures, reduced variability and skewness, and increased complexity of reaction time series after 6 weeks of treatment, while nonresponders showed no significant changes. Prior to treatment, responders had significantly higher variability and skewness, combined with lower complexity, compared with nonresponders. Conclusion: These results show that the CPT test is useful in the evaluation of treatment response to MPH.

Review of Clinical Outcome Assessments in Pediatric Attention-Deficit/Hyperactivity Disorder

PURPOSE

Various clinical outcome assessments (COAs) are used in clinical research to assess and monitor treatment efficacy in pediatric attention-deficit/hyperactivity disorder (ADHD) trials. It is unclear whether the concepts assessed are those that are important to patients and their caregivers. The concepts measured by commonly used COAs in this population have not been explicitly compared.

METHODS

We conducted reviews of the qualitative literature to extract information on pediatric ADHD-related concepts reported by pediatric patients, parents, and teachers. Using these concepts, we developed a conceptual framework of pediatric ADHD using both the Diagnostic and Statistical Manual of Mental Disorders (DSM) criteria and the additional symptoms and behavioral impacts identified in the literature. We searched for COAs that have been used in pediatric ADHD research and mapped their items based on their conceptual underpinning.

RESULTS

Of the 27 COAs found in the empirical literature, 4 COAs assessed only DSM symptoms. The most comprehensive coverage of our conceptual framework was seen in the Swanson, Nolan, and Pelham Rating Scale-DSM-IV (SNAP-IV). Eighteen COAs were used in at least 1 clinical trial: ADHD-Rating Scale-IV (ADHD-RS-IV) was used most often (n=77), followed by SNAP-IV (n=50), Swanson, Kotkin, Agler, M-Flynn, and Pelham Scale (SKAMP; n=31), Weiss Functional Impairment Rating Scale (WFIRS; n=24), and Vanderbilt ADHD Diagnostic Rating Scale (VADRS; n=15).

CONCLUSION

We identified symptoms and behavioral impacts from qualitative studies in pediatric ADHD that are not included in DSM-based criteria. Most COAs used in pediatric ADHD clinical trials measure only those symptoms listed in the DSM. While these COAs can measure symptom severity, they may not assess the full range of symptoms and impacts important to patients and their caregivers. Future research is needed to measure all concepts important to patients and caregivers within ADHD clinical trials.

Health state utilities for infertility and subfertility

Background

Health state utility values allow for comparison of treatments across different diseases. Utility values for fertility-impaired health states are currently unavailable. Such values are necessary in order to determine the relative costs-effectiveness of fertility treatments.

Methods

This study aimed to determine utility weights for infertile and subfertile health states. In addition, it explored the Dutch general population’s opinions regarding the inclusion of infertility treatments in the Dutch health insurers’ basic benefit package. An online questionnaire was designed to determine the health-related quality of life values of six fertility-impaired health states. The study population consisted of a representative sample of the Dutch adult population. Respondents were asked to evaluate the health states through direct health valuation methods, i.e. the Visual Analogue Scale (VAS) and the Time Trade-Off (TTO) method. In addition, respondents were asked about their opinions regarding reimbursement of fertility-related treatments.

Results

The respondents’ (n = 767) VAS scores ranged from 0.640 to 0.796. TTO utility values ranged from 0.792 to 0.868. Primary infertility and subfertility was valued lower than secondary infertility and subfertility. In total, 92% of the respondents stated that fertility treatments should be fully or partially reimbursed by the health insurance basic benefit package.

Conclusions

Having fertility problems results in substantial disutilities according to the viewpoint of the Dutch general population. The results make it possible to compare the value for money of infertility treatment to that of treatments in other disease areas. There is strong support among the general population for reimbursing fertility treatments through the Dutch basic benefit package.

The time horizon matters: results of an exploratory study varying the timeframe in time trade-off and standard gamble utility elicitation

INTRODUCTION

The purpose of this study was to examine whether the time horizon of time trade-off (TTO) and standard gamble (SG) utility assessment influences utility scores and discrimination between health states.

METHODS

In two phases, UK general population participants rated three osteoarthritis health states in TTO and SG procedures with two time horizons: (1) 10-year and (2) a time horizon derived from self-reported additional life expectancy (ALE). The two time horizons were compared in terms of mean utilities and discrimination among health states.

RESULTS

In Phase 1, the 10-year tasks were completed by 80 participants, 35 of whom also completed utility assessment with the ALE. In Phase 2, all 101 participants completed procedures with both time horizons. Utility scores tended to be lower with the ALE than the 10-year, a difference that was statistically significant for two health states with SG in Phase 1 (P < 0.05), two health states with TTO in Phase 2 (P < 0.01), and one health state with SG in Phase 2 (P < 0.001). In Phase 1, rates of discrimination between mild and moderate osteoarthritis health states were significantly higher with the ALE than the 10-year (TTO: P = 0.03; SG: P = 0.001). This pattern of discrimination was similar in Phase 2.

DISCUSSION

Results suggest that the time horizon could influence utility scores and discrimination among health states. When designing utility evaluations, researchers should carefully consider the time horizon so that the value of health states is accurately represented in cost-utility models.

Is adjunctive pharmacotherapy in attention-deficit/hyperactivity disorder cost-effective in Canada: a cost-effectiveness assessment of guanfacine extended-release as an adjunctive therapy to a long-acting stimulant for the treatment of ADHD

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is a common psychiatric disorder in children, with worldwide prevalence of ADHD varying from 5.9 to 7.1 %, depending on the reporter. In case of inadequate response to stimulants, combination therapy of stimulants and an adjunctive medication may improve the control of ADHD symptoms, reduce the dose-limiting adverse events, and help control comorbidities. To date, the only medication to be used for adjunctive therapy to psychostimulants is guanfacine extended release (GXR). The aim of this study was to assess the economic impact of GXR as an adjunct therapy with long-acting stimulants (GXR + stimulant) compared to long-acting stimulant monotherapy (stimulant alone) in the treatment of children and adolescents with ADHD in Canada.

METHOD

A Markov model was developed using health states defined based on the clinician-reported Clinical Global Impression-Severity (CGI-S) score (normal, mild, moderate, severe). Transition probabilities were calculated based on patient-level data from a published study. Long-acting stimulants available in Canada were considered in the base-case model: amphetamine mixed salts, methylphenidate HCl formulations, and lisdexamfetamine dimesylate. Analyses were conducted from a Canadian Ministry of Health (MoH; Ontario) and a societal perspective over a 1-year time horizon with weekly cycles.

RESULTS

Over a 1-year time horizon, GXR + stimulant was associated with 0.655 quality-adjusted life year (QALY), compared to 0.627 QALY with stimulant alone, for a gain of 0.028 QALY. From a MoH perspective, GXR+ stimulant and stimulant alone were associated with total costs of $CA1,617 and $CA949, respectively (difference of $CA668), which resulted in an incremental cost-effectiveness ratio (ICER) of $CA23,720/QALY. From a societal perspective, GXR + stimulant and stimulant alone were associated with total costs of $CA3,915 and $CA3,582, respectively (difference of $CA334), which resulted in an ICER of $CA11,845/QALY. Probabilistic sensitivity analysis (PSA) of GXR + stimulant showed that it remains a cost-effective strategy in 100 % of the simulations from both perspectives in numerous PSA and one-way sensitivity analyses, relative to a willingness to pay threshold of $50,000/QALY.

CONCLUSIONS

This economic evaluation demonstrates that GXR +  stimulant is cost-effective compared to stimulant alone in the treatment of children and adolescents with ADHD in Canada.

The impact of ADHD on the health and well-being of ADHD children and their siblings

Childhood attention-deficit/hyperactivity disorder (ADHD) has been associated with reduced health and well-being of patients and their families. The authors undertook a large UK survey-based observational study of the burden associated with childhood ADHD. The impact of ADHD on both the patient (N = 476) and their siblings (N = 337) on health-related quality of life (HRQoL) and happiness was quantified using multiple standard measures [e.g. child health utility-9D (CHU-9D), EuroQol-5D-Youth]. In the analysis, careful statistical adjustments were made to ensure a like-for-like comparison of ADHD families with two different control groups. We controlled for carers' ADHD symptoms, their employment and relationship status and siblings' ADHD symptoms. ADHD was associated with a significant deficit in the patient's HRQoL (with a CHU-9D score of around 6 % lower). Children with ADHD also have less sleep and were less happy with their family and their lives overall. No consistent decrement to the HRQoL of the siblings was identified across the models, except that related to their own conduct problems. The siblings do, however, report lower happiness with life overall and with their family, even when controlling for the siblings own ADHD symptoms. We also find evidence of elevated bullying between siblings in families with a child with ADHD. Overall, the current results suggest that the reduction in quality of life caused by ADHD is experienced both by the child with ADHD and their siblings.

A Cost-Utility Analysis of Lisdexamfetamine Versus Atomoxetine in the Treatment of Children and Adolescents with Attention-Deficit/Hyperactivity Disorder and Inadequate Response to Methylphenidate

BACKGROUND

An economic analysis from the perspective of the UK National Health Service (NHS) evaluated the cost effectiveness of lisdexamfetamine dimesylate (LDX) compared with atomoxetine in children and adolescents with attention-deficit/hyperactivity disorder who have had an inadequate response to methylphenidate.

METHODS

A 1-year decision-analytic model was constructed, with the health outcomes "response", "nonresponse", and "unable to tolerate". Clinical data were taken from a head-to-head, randomized controlled trial in inadequate responders to methylphenidate. Response to treatment was defined as a score of 1 (very much improved) or 2 (much improved) on the Clinical Global Impression-Improvement subscale. Tolerability was assessed by discontinuation rates owing to adverse events. Utility weights were identified via a systematic literature review. Healthcare resource use estimates were obtained via a survey of clinicians. Daily drug costs were derived from British National Formulary 2012 costs and mean doses reported in the trial. One-way and probabilistic sensitivity analyses (PSAs) were performed.

RESULTS

The comparison of LDX with atomoxetine resulted in an estimate of an incremental cost-effectiveness ratio of £1802 per quality-adjusted life-year (QALY). The result was robust in a wide range of sensitivity analyses; results were most sensitive to changes in drug costs and efficacy. In the PSA, assuming a maximum willingness to pay of £20,000 per QALY, LDX versus atomoxetine had an 86 % probability of being cost effective. In 38 % of PSA runs, LDX was more effective and less costly than atomoxetine.

CONCLUSIONS

From the perspective of the UK NHS, LDX provides a cost-effective treatment option for children and adolescents who are inadequate responders to methylphenidate.

Cost-effectiveness of extended-release methylphenidate in children and adolescents with attention-deficit/hyperactivity disorder sub-optimally treated with immediate release methylphenidate

BACKGROUND

Attention-Deficit/Hyperactivity Disorder (ADHD) is a common psychiatric disorder in children and adolescents. Immediate-release methylphenidate (IR-MPH) is the medical treatment of first choice. The necessity to use several IR-MPH tablets per day and associated potential social stigma at school often leads to reduced compliance, sub-optimal treatment, and therefore economic loss. Replacement of IR-MPH with a single-dose extended release (ER-MPH) formulation may improve drug response and economic efficiency.

OBJECTIVE

To evaluate the cost-effectiveness from a societal perspective of a switch from IR-MPH to ER-MPH in patients who are sub-optimally treated.

METHODS

A daily Markov-cycle model covering a time-span of 10 years was developed including four different health states: (1) optimal response, (2) sub-optimal response, (3) discontinued treatment, and (4) natural remission. ER-MPH options included methylphenidate osmotic release oral system (MPH-OROS) and Equasym XL/Medikinet CR. Both direct costs and indirect costs were included in the analysis, and effects were expressed as quality-adjusted life years (QALYs). Univariate, multivariate as well as probabilistic sensitivity analysis were conducted and the main outcomes were incremental cost-effectiveness ratios.

RESULTS

Switching sub-optimally treated patients from IR-MPH to MPH-OROS or Equasym XL/Medikinet CR led to per-patient cost-savings of €4200 and €5400, respectively, over a 10-year treatment span. Sensitivity analysis with plausible variations of input parameters resulted in cost-savings in the vast majority of estimations.

CONCLUSIONS

This study lends economic support to switching patients with ADHD with suboptimal response to short-acting IR-MPH to long-acting ER-MPH regimens.

Study protocol for a randomized controlled trial comparing the efficacy of a specialist and a generic parenting programme for the treatment of preschool ADHD

Background

The New Forest Parenting Programme (NFPP) is a home-delivered, evidence-based parenting programme to target symptoms of attention-deficit/hyperactivity disorder (ADHD) in preschool children. It has been adapted for use with ‘hard-to-reach’ or ‘difficult-to-treat’ children. This trial will compare the adapted-NFPP with a generic parenting group-based programme, Incredible Years (IY), which has been recommended for children with preschool-type ADHD symptoms.

Methods/design

This multicentre randomized controlled trial comprises three arms: adapted-NFPP, IY and treatment as usual (TAU). A sample of 329 parents of preschool-aged children with a research diagnosis of ADHD enriched for hard-to-reach and potentially treatment-resistant children will be allocated to the arms in the ratio 3:3:1. Participants in the adapted-NFPP and IY arms receive an induction visit followed by 12 weekly parenting sessions of 1½ hours (adapted-NFPP) or 2½ hours (IY) over 2.5 years. Adapted-NFPP will be delivered as a one-to-one home-based intervention; IY, as a group-based intervention. TAU participants are offered a parenting programme at the end of the study. The primary objective is to test whether the adapted-NFPP produces beneficial effects in terms of core ADHD symptoms. Secondary objectives include examination of the treatment impact on secondary outcomes, a study of cost-effectiveness and examination of the mediating role of treatment-induced changes in parenting behaviour and neuropsychological function. The primary outcome is change in ADHD symptoms, as measured by the parent-completed version of the SNAP-IV questionnaire, adjusted for pretreatment SNAP-IV score. Secondary outcome measures are: a validated index of behaviour during child’s solo play; teacher-reported SNAP-IV (ADHD scale); teacher and parent SNAP-IV (ODD) Scale; Eyberg Child Behaviour Inventory - Oppositional Defiant Disorder scale; Revised Client Service Receipt Inventory - Health Economics Costs measure and EuroQol (EQ5D) health-related quality-of-life measure. Follow-up measures will be collected 6 months after treatment for participants allocated to adapted-NFPP and IY.

Discussion

This trial will provide evidence as to whether the adapted-NFPP is more effective and cost-effective than the recommended treatment and TAU. It will also provide information about mediating factors (improved parenting and neuropsychological function) and moderating factors (parent and child genetic factors) in any increased benefit.

Trial registration

Current Controlled Trials, ISRCTN39288126.

Health state utilities associated with adult attention-deficit/hyperactivity disorder

OBJECTIVES

With growing awareness of the importance of adult attention-deficit/hyperactivity disorder (ADHD) treatment, cost-effectiveness analyses, including utilities, are needed to compare the value of treatment options. Although utilities have been reported for childhood ADHD, little is known about utilities representing adult ADHD. Therefore, the purpose of this study was to estimate utilities associated with adult ADHD.

METHODS

Health-state descriptions of adult ADHD were drafted based on literature review, interviews with four clinicians, and clinical trial data. Health states were revised based on a pilot study with 26 participants. Final health states were rated in time trade-off interviews with general population respondents in London and Edinburgh, UK.

RESULTS

A total of 158 participants completed interviews (mean age =47.0 years; 49.4% female; Edinburgh =80 participants). Mean (standard deviation [SD]) utilities were 0.82 (0.17), 0.68 (0.28), and 0.67 (0.28) for health states describing treatment responders (health state A), nonresponders (health state B), and untreated patients (health state C), respectively. Most participants rated health state A as preferable to B (n=92; 58.2%) and C (n=97; 61.4%). The majority rated B and C as equal (n=125; 79.1%). Paired Student's t-tests found that A had a significantly greater mean utility than B (t=10.0; P<0.0001) and C (t=10.2; P<0.0001).

CONCLUSION

The current study provides utilities that may be used in cost-utility models of treatment for adult ADHD. Results reflected clear differences between health states representing treatment responders and nonresponders/untreated patients. Current utilities were comparable to those previously reported for childhood ADHD.

Elicitation of health state utilities in soft tissue sarcoma

PURPOSE

Soft tissue sarcomas (STS) are uncommon tumours with varying histological subtypes. There is a paucity of available data concerning the quality-of-life (QoL) impact of STS which could be used to support economic evaluation of future treatments. This study aimed to elicit societal utility values for health states that depict the impact of STS and its treatment.

METHODS

Following the development of eight health state vignettes, a sample of 100 members of the UK general public participated in a valuation exercise to elicit utility values using the time trade-off procedure.

RESULTS

The treatment response state was valued as the least burdensome by participants followed by the prospect of stable disease (mean utility value: 0.736 SD 0.21). Serious adverse events were associated with a range of disutilities from -0.236 for grade III/IV pain to -0.357 for grade III/IV nausea/vomiting. Progressive disease was deemed the least desirable outcome and was associated with a substantial decline in utility (-0.473).

CONCLUSIONS

Findings suggest advanced STS are associated with significant burden for individuals. Treatment-related adverse events were seen as debilitating, however, progression represents an enormous challenge to QoL. This illustrates the significant value to individuals of extending the progression free survival period.

Cost effectiveness of guanfacine extended release as an adjunctive therapy to a stimulant compared with stimulant monotherapy for the treatment of attention-deficit hyperactivity disorder in children and adolescents

BACKGROUND

Attention-deficit hyperactivity disorder (ADHD) is a common psychiatric disorder in childhood, affecting 3-7% of school-age children in the US and imposing substantial economic burden. Stimulants are considered first-line pharmacological treatment and are the most prescribed treatment for ADHD. However, approximately 30% of children with ADHD do not have an optimal response to a single stimulant and may require adjunctive therapy.

OBJECTIVE

Our objective was to conduct a cost-effectiveness analysis (CEA) of adding a non-stimulant, guanfacine extended release (GXR), to stimulants versus maintaining existing stimulant monotherapy in the treatment of ADHD in children and adolescents with suboptimal response to stimulant monotherapy.

METHODS

A 1-year Markov model was developed to estimate costs and effectiveness from a US third-party payer perspective. Effectiveness was measured by the QALY. The model assumed that patients transitioned among four health states (normal, mild, moderate and severe), defined by the Clinical Global Impression-Severity (CGI-S) scale. Transition probabilities were estimated in an ordered logit model using patient-level data from a multicentre, 9-week, double-blind, placebo-controlled, dose-optimization study, where subjects (n = 461) continued their stable morning stimulant and were randomized to GXR administered in the morning, GXR administered in the evening, or placebo. The model assumed that patients in moderate/severe health states after week 8 would discontinue ADHD treatment and remain in that state for the rest of the study period. Direct costs included drug wholesale acquisition costs and health state costs, all in $US, year 2010 values. Utility associated with each health state was obtained from the literature and disutilities associated with adverse events were applied for the first 4 weeks. One-way sensitivity analyses and probabilistic sensitivity analysis (PSA) were conducted by varying costs, utilities, adverse-event duration, and transition probabilities.

RESULTS

Compared with maintaining existing stimulant monotherapy, adding GXR to existing stimulant monotherapy was associated with an incremental drug cost of $US1016 but a lower medical cost of $US124, resulting in a total incremental cost of $US892 at 1 year. The addition of GXR to stimulants led to an incremental QALY of 0.03 and an incremental cost-effectiveness ratio (ICER) of $US31,660/QALY. In one-way sensitivity analysis, ICER values ranged from $US19,723, when 100% of patients were assumed to be severe in their initial health state, to $US46,631, when the last observed states from the clinical trial were carried forward to the end of the 1-year analysis period. PSA demonstrated a 94.6% likelihood that the ICER falls below $US50,000/QALY.

CONCLUSIONS

The impairment associated with residual ADHD symptoms after stimulant therapy is becoming increasingly recognized. This is the first analysis of the cost effectiveness of stimulants combined with an adjunctive medication. This study suggests that the adjunctive therapy of GXR with stimulants is a cost-effective treatment based on a willingness-to-pay threshold of $US50,000/QALY. This may address an unmet need among patients with suboptimal response to stimulant monotherapy.