Analysis, sample size, and power for estimating incremental net health benefit from clinical trial data

Effects of monopolar pulsed-capacitive dielectric radiofrequency diathermy in patients with chronic low back pain: a randomised clinical trial

Monopolar capacitive diathermy is a physiotherapy technique that uses high-frequency currents to generate heat in deep tissues. This heat can have several therapeutic effects, especially in the treatment of chronic low back pain (CLBP), however, until now there is little evidence of this type of diathermy. The purpose was to evaluate the efficacy of a pulsed monopolar dielectric radiofrequency diathermy (PRF)-capacitive type versus simulated treatment on symptomatology of patients with CLBP. A single-blind randomised controlled trial was conducted. Sixty patients with CLBP were randomly assigned to a PRF-capacitive or a simulated treatment group. All participants received 3 sessions per week for 3 weeks. Disability, pain intensity, movement phobia, lumbar anteflexion, quality of life, and sleep quality were assessed at baseline, after treatment, and at two months. The application of 9 sessions of PRF-capacitive showed significant improvements compared to simulated therapy during the entire follow-up for disability (F = 26.99, p < 0.001), pain intensity (F = 0.550, p < 0.001), the quality of life components of physical function (F = 0.780, p < 0.001), social function (F = 0.780, p < 0.001) and mental health (F = 0.858, p = 0.003) and for sleep duration (F = 0.863, p = 0.004).

Electrical dry needling versus a non-invasive multicomponent intervention in the treatment of myofascial trigger points in patients with chronic low back pain: A randomised clinical trial

OBJECTIVE

To compare the effects of electrical dry needling with a non-invasive multi-component intervention in patients with chronic low back pain.

DESIGN

A randomised single-blind clinical trial.

SETTING

Outpatient Physiotherapy Clinic; home.

PARTICIPANTS

Sixty-four patients with chronic low back pain aged 30-65 years.

INTERVENTIONS

Six-week electrical dry needling on myofascial trigger points, and a non-invasive multicomponent intervention (home exercise programme, stretching and ischemic compression).

MAIN MEASURES

Pain (Visual Analogue Scale), disability (Roland-Morris Disability Questionnaire and Oswestry Disability Index), kinesiophobia (Tampa Scale of Kinesiophobia), quality of life and sleep (Short Form 36-item Health Survey and Pittsburgh Sleep Quality Index), isometric endurance of trunk flexor muscles (McQuade test), lumbar mobility in flexion (finger-to-floor distance), and pressure pain threshold (algometer) were assessed at baseline, after 6 weeks, and after 2 months.

RESULTS

ANOVA showed statistically significant differences in group-by-time interaction for most pain pressure thresholds of myofascial trigger points (P < 0.05), for disability (Roland-Morris Disability Questionnaire: F = 6.14, P = 0.016; and Oswestry Disability Index: F = 7.36, P = 0.009), for trunk anteflexion (F = 10.03, P = 0.002) and for habitual sleep efficacy (F = 6.65, P = 0.012), use of hypnotics (F = 4.77, P = 0.033) and total score of quality of sleep (F = 8.23, P = 0.006).

CONCLUSIONS

In comparison to a non-invasive multicomponent intervention, electrical dry needling has more positive effects on disability, pain intensity, kinesiophobia, and reducing patients' sensitivity to myofascial trigger points pressure, at post-treatment and at 2 months.

CLINICAL TRIAL REGISTRATION NUMBER

NCT04804228. Registered on May 28th, 2021. Available at https://clinicaltrials.gov/ct2/show/NCT04804228.

Power and sample size calculation for incremental net benefit in cost effectiveness analyses with applications to trials conducted by the Canadian Cancer Trials Group

BACKGROUND

Historically, a priori power and sample size calculations have not been routinely performed cost-effectiveness analyses (CEA), partly because the absence of published cost and effectiveness correlation and variance data, which are essential for power and sample size calculations. Importantly, the empirical correlation between cost and effectiveness has not been examined with respect to the estimation of value-for-money in clinical literature. Therefore, it is not well established if cost-effectiveness studies embedded within randomized-controlled-trials (RCTs) are under- or over-powered to detect changes in value-for-money. However, recently guidelines (such as those from ISPOR) and funding agencies have suggested sample size and power calculations should be considered in CEAs embedded in clinical trials.

METHODS

We examined all RCTs conducted by the Canadian Cancer Trials Group with an embedded cost-effectiveness analysis. Variance and correlation of effectiveness and costs were derived from original-trial data. The incremental net benefit method was used to calculate the power of the cost-effectiveness analysis, with exploration of alternative correlation and willingness-to-pay values.

RESULTS

We identified four trials for inclusion. We observed that a hypothetical scenario of correlation coefficient of zero between cost and effectiveness led to a conservative estimate of sample size. The cost-effectiveness analysis was under-powered to detect changes in value-for-money in two trials, at willingness-to-pay of $100,000. Based on our observations, we present six considerations for future economic evaluations, and an online program to help analysts include a priori sample size and power calculations in future clinical trials.

CONCLUSION

The correlation between cost and effectiveness had a potentially meaningful impact on the power and variance of value-for-money estimates in the examined cost-effectiveness analyses. Therefore, the six considerations and online program, may facilitate a priori power calculations in embedded cost-effectiveness analyses in future clinical trials.

Electrical dry needling versus conventional physiotherapy in the treatment of active and latent myofascial trigger points in patients with nonspecific chronic low back pain

Background

Chronic low back pain is considered to be one of the main causes of absenteeism from work and primary and specialized consultations. The symptoms of nonspecific chronic low back pain may be accompanied by the activation of myofascial trigger points in the muscles, together with local and/or referred pain. Electrical dry needling is increasingly used in the treatment of lumbar myofascial pain. Conventional physiotherapy, however, is a popular approach to chronic pathologies, and there is evidence of different modalities of physiotherapy being used in the treatment of chronic low back pain. The aim of this study has been to determine the effectiveness of electrical dry needling versus conventional physiotherapy when applied to active and latent myofascial trigger points in patients with nonspecific chronic low back pain.

Methods

This is a controlled, randomized, two-arm, double-blind study. A total of 92 patients with chronic low back pain (time to onset ≥ 3 months, Roland Morris Disability Questionnaire score ≥ 4) will be recruited from the University of Almería. Participants will be divided into two study groups (n = 40) to receive treatment of low back pain with electrical dry needling and conventional physiotherapy (ischaemic compression, analytic stretching and postural education training dossier). A total of 6 sessions will be administered once a week for 6 weeks. Pain intensity, disability, fear of movement, quality of life, quality of sleep, anxiety and depression, pressure pain threshold, abdominal strength and lumbar mobility will be recorded at 6 weeks (post-immediate) and 2 months after the end of treatment.

Discussion

We believe that an approach including electrical dry needling to chronic low back pain dysfunction will be more effective in these patients. The results of this study will inform clinicians on which type of treatment is more beneficial for patients with chronic low back pain.

Trial registration

ClinicalTrials.gov NCT04804228. Registered on 14 January 2021

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06179-y.

Comparing an e-Health program vs home rehabilitation program in patients with non-specific low back pain: A study protocol randomized feasibility trial

BACKGROUND

There is little evidence on the reliability of the web application-based rehabilitation systems to treat chronic low back pain (CLBP).

METHODS

This protocol describes a double-blind, randomized controlled feasibility trial of an e-Health intervention developed to support the self-management of people with CLBP in primary care physiotherapy. Three Hospitals with primary care for outpatients will be the units of randomisation, in each Hospital the participants will be randomized to one of two groups, a pragmatic control group receiving either the usual home program based on electrostimulation and McKenzie Therapy and e-Health intervention. Patients are followed up at 2 and 6 months. The primary outcomes are (1) acceptability and demand of the intervention by GPs, physiotherapists and patients and (2) feasibility and optimal study design/methods for a definitive trial. Secondary outcomes will include analysis in the clinical outcomes of pain, disability, fear of movement, quality of life, isometric resistance of the trunk flexors, lumbar anteflexion and lumbar segmental range of motion.

DISCUSSION

The specific e-Health programs to home could increase adherence to treatment, prevent stages of greater pain and disability, and improve the painful symptomatology.

CONCLUSIONS

The e-Health programs could be an effective healthcare tool that can reach a large number of people living in rural or remote areas.

Comparison of the effectiveness of an e-health program versus a home rehabilitation program in patients with chronic low back pain: A double blind randomized controlled trial

OBJETIVE

We conducted a randomized double blind clinical trial, to compare the effectiveness of McKenzie exercises and electroanalgesia via an e-Health program versus a home rehabilitation program on functionality, pain, fear of movement and quality of life in patients with non-specific chronic low back pain.

METHODS

Seventy-four participants with non-specific chronic low back pain were randomized to either the e- Health program group (n = 39) or the home rehabilitation program group (n = 35). The interventions consisted of the e-Health program group performing McKenzie exercises and received transcutaneous electrical nerve stimulation, while the home rehabilitation group attended an information session to explain the exercises, which they then performed at home with printed instructions. Both groups performed 3 weekly sessions for 8 weeks. The following were analyzed main measures: pain, disability, fear of movement, quality of life, trunk muscle endurance and trunk anteflexion motion were assessed at baseline and at 2 months.

RESULTS

Independent samples Student's t-tests showed that although the patients who followed the e-Health program showed significantly greater improvement than those who followed the home disability rehabilitation program in terms of intensity of pain, lumbar flexion mobility (P < 0.001), and the following dimensions of quality of life (P < 0.005), both groups improved significantly in the immediate post-treatment follow up compared with baseline scores.

CONCLUSIONS

Patients with chronic low back pain who followed an unsupervised home intervention supported by an individualized video exercise program showed greater post-treatment improvement than those who followed the same program with printed instructions.

Correlation of plasma and urine Wnt5A with the disease activity and cutaneous lesion severity in patients with systemic lupus erythematosus

Reliable noninvasive biomarkers are needed to accurately assess disease activity and prognosis in patients with systemic lupus erythematosus (SLE). The purpose of this study was to investigate the clinical relevance of Wnt5A with disease activity and severity with cutaneous involvement in particular in SLE patients; its concentrations in plasma and urine were examined and analyzed. In the cross-sectional study, the clinical relevance of Wnt5A protein was evaluated in both plasma and urine of SLE patients and healthy cohorts using commercial enzyme-linked immunosorbent assays (ELISA). Significantly, more abundances of Wnt5A protein were determined in both of plasmas and urines of SLE patients compared to healthy cohorts (p < 0.0001), which were even higher in active disease (AD) SLE patients relative to low disease activity (LDA) SLE patients (p < 0.0001). Meanwhile, the ROC curve analysis demonstrated that the plasma and urine Wnt5A were potential candidate biomarkers for identifying the disease activity and severity in SLE patients. The discriminant function analysis further revealed that the plasma and urine Wnt5A were separated and distinct for AD SLE patients and healthy controls. In consistence, the disease severity was correlated with the plasma and urine Wnt5A as ascertained by CLASI activity score and the prevalence of serositis in SLE patients. These results suggest that Wnt5A, as a summary measure for different inflammatory processes, could be a potential biomarker for accessing the disease activity, and a noninvasive biomarker for evaluating the disease severity in terms of cutaneous involvement in SLE patients.

Study protocol randomised controlled trial comparison of cost-utility and cost-effectiveness of a face-to-face rehabilitation programme versus a telemedicine programme in the treatment of patients with chronic low back pain

INTRODUCTION

Chronic lower back pain is a highly prevalent medical condition in Western countries, which that incurs a considerable social and economic burden. Although prescription exercise at home for chronic pain has become a widely used alternative to reduce healthcare costs, the evidence regarding patient adherence and decreased in costs in European countries is scarce and inconclusive. The objective of this study is to examine the cost-utility and cost-effectiveness in patients with chronic lower back pain treated with the McKenzie Method and electroanalgesia via a telemedicine programme versus a face-to-face programme.

METHODS AND ANALYSIS

This study reports the protocol for a randomised, two-arm, multicentre, parallel controlled trial. A total of 540 patients with chronic lower back pain (onset time ≥3 months, Roland Morris Disability Questionnaire ≥4) will be recruited in three hospitals in Andalusia. Participants will be assigned to one of two groups (n=270, respectively) to receive electroanalgesia and Mckenzie method exercises through a telemedicine or a face-to-face programme. A total of 24 sessions will be administered three times a week for 8 weeks. Since the study design does not allow participant blinding, the outcome assessor and the statistician will be blinded. Use of helth care resources and costs due to work absenteeism will be captured and analysed. In addition, pain, intensity, fear of movement, quality of life and strength of the core muscle and anteflexion lumbar will be recorded at 2 and 6 months after the start of treatment.

ETHICS AND DISSEMINATION

Human Research and Local Ethics Committee of the 'Hospital Complex Torrecárdenas of Almeria, University Hospital of Granada and Virgen Macarena de Sevilla Hospital-Andalusian Health Service'. Study findings will be released to the research, clinical and health service through publication in international journals and conferences.

TRIAL REGISTRATION NUMBER

NCT04266366.

Cognitive behavioral therapy for insomnia in stable heart failure: Protocol for a randomized controlled trial

BACKGROUND

Chronic insomnia is associated with disabling symptoms and decrements in functional performance. It may contribute to the development of heart failure (HF) and incident mortality. In our previous work, cognitive-behavioral therapy for insomnia (CBT-I), compared to HF self-management education, provided as an attention control condition, was feasible, acceptable, and had large effects on insomnia and fatigue among HF patients.

OBJECTIVES

The purpose of this randomized controlled trial (RCT) is to evaluate the sustained effects of group CBT-I compared with HF self-management education (attention control) on insomnia severity, sleep characteristics, daytime symptoms, symptom clusters, functional performance, and health care utilization among patients with stable HF. We will estimate the cost-effectiveness of CBT-I and explore the effects of CBT-I on event-free survival (EFS).

METHODS

Two hundred participants will be randomized in clusters to a single center parallel group (CBT-I vs. attention control) RCT. Wrist actigraphy and self-report will elicit insomnia, sleep characteristics, symptoms, and functional performance. We will use the psychomotor vigilance test to evaluate sleep loss effects and the Six Minute Walk Test to evaluate effects on daytime function. Medical record review and interviews will elicit health care utilization and EFS. Statistical methods will include general linear mixed models and latent transition analysis. Stochastic cost-effectiveness analysis with a competing risk approach will be employed to conduct the cost-effectiveness analysis.

DISCUSSION

The results will be generalizable to HF patients with chronic comorbid insomnia and pave the way for future research focused on the dissemination and translation of CBT-I into HF settings.

Cost-effectiveness of a voucher-based intervention for smoking cessation

BACKGROUND

Contingency management (CM) has been shown to be effective in reducing smoking consumption, but has traditionally been criticized for its costs.

OBJECTIVES

This study assessed the cost-effectiveness of using a voucher-based CM protocol added to a cognitive behavioral treatment (CBT) for smoking cessation among treatment-seeking patients from the general population.

METHODS

A total of 92 patients were randomly assigned to CBT or CBT plus CM for abstinence. Incremental cost-effectiveness ratios (ICERs) were calculated by dividing the increase in costs by the increase in effects (continuous abstinence, longest duration of abstinence at 6-month follow-up and cotinine results during the treatment). An acceptability curve illustrated the statistical uncertainty surrounding the cost-effectiveness estimate. We also determined the optimum cost per participant for predicting the smoking status at 6-month follow-up.

RESULTS

The average cost per participant in the CBT condition was €138.73 (US$ 150.23) as opposed to €411.61 (US$ 445.73) in the CBT plus CM condition (p < 0.01). The incremental cost of using voucher-based CM to increase the number of participants that maintained abstinence at 6-month follow-up by one extra participant was €68.22 (US$ 73.88), and to lengthen the longest duration of abstinence by 1 week was €53.92 (US$ 58.39). The incremental cost to obtain an extra cotinine-negative result was €181.90 (US$ 196.98).

CONCLUSION

Compared with CBT alone, the voucher-based protocol required additional costs but achieved significantly better outcomes. These results will allow stakeholders to make policy decisions about CM implementation for smoking cessation in the broader community.

Symptom- and fraction of exhaled nitric oxide-driven strategies for asthma control: A cluster-randomized trial in primary care

BACKGROUND

Aiming at partly controlled asthma (PCa) instead of controlled asthma (Ca) might decrease asthma medication use. Biomarkers, such as the fraction of exhaled nitric oxide (Feno), allow further tailoring of treatment.

OBJECTIVE

We sought to assess the cost-effectiveness and clinical effectiveness of pursuing PCa, Ca, or Feno-driven controlled asthma (FCa).

METHODS

In a nonblind, pragmatic, cluster-randomized trial in primary care, adults (18-50 years of age) with a doctor's diagnosis of asthma who were prescribed inhaled corticosteroids were allocated to one of 3 treatment strategies: (1) aiming at PCa (Asthma Control Questionnaire [ACQ] score <1.50); (2) aiming at Ca (ACQ score <0.75); and (3) aiming at FCa (ACQ score <0.75 and Feno value <25 ppb). During 12 months' follow-up, treatment was adjusted every 3 months by using an online decision support tool. Outcomes were incremental cost per quality-adjusted life year gained, asthma control (ACQ score), quality of life (Asthma Quality of Life Questionnaire score), asthma medication use, and severe exacerbation rate.

RESULTS

Six hundred eleven participants were allocated to the PCa (n = 219), Ca (n = 203), or FCa (n = 189) strategies. The FCa strategy improved asthma control compared with the PCa strategy (P < .02). There were no differences in quality of life (P ≥ .36). Asthma medication use was significantly lower for the PCa and FCa strategies compared with the Ca strategy (medication costs: PCa, $452; Ca, $551; and FCa, $456; P ≤ .04). The FCa strategy had the highest probability of cost-effectiveness at a willingness to pay of $50,000/quality-adjusted life year (86%; PCa, 2%; Ca, 12%). There were no differences in severe exacerbation rate.

CONCLUSION

A symptom- plus Feno-driven strategy reduces asthma medication use while sustaining asthma control and quality of life and is the preferred strategy for adult asthmatic patients in primary care.

A C++ program to calculate sample sizes for cost-effectiveness trials in a Bayesian framework

Cost-Effectiveness Analysis (CEA) has become an increasingly important component of clinical trials. However, formal sample size calculations for such studies are not common. One of the reasons for this might be due to the absence of readily available computer software to perform complex calculations, particularly in a Bayesian setting. In this paper, a C++ program (using NAG library functions/subroutines) is presented to estimate the sample sizes for cost-effectiveness clinical trials in a Bayesian framework. The program can equally be used to calculate sample sizes for efficacy trials. The Bayesian approach to sample size calculation is based on that of O'Hagan and Stevens (A. O'Hagan, J.W. Stevens, Bayesian assessment of sample size for clinical trials of cost-effectiveness, Medical Decision Making 21 (2001) 219-230). With this program, the user can calculate sample sizes for various thresholds of willingness to pay and under various assumptions of the correlations between cost and effects. Under some prior, the program produces frequentist sample size as well. The program runs under windows environment and running time is very short.

Cost-utility analysis of a dance intervention for adolescent girls with internalizing problems

BACKGROUND

The increasing prevalence of psychological health problems among adolescent girls is alarming. Knowledge of beneficial effects of physical activity on psychological health is widespread. Dance is a popular form of exercise that could be a protective factor in preventing and treating symptoms of depression. The aim of this study was to assess the cost-effectiveness of a dance intervention in addition to usual school health services for adolescent girls with internalizing problems, compared with usual school health services alone.

METHODS

A cost-utility analysis from a societal perspective based on a randomized controlled intervention trial was performed. The setting was a city in central Sweden with a population of 130 000. A total of 112 adolescent girls, 13-18 years old, with internalizing problems participated in the study. They were randomly assigned to intervention (n = 59) or control (n = 53) group. The intervention comprised dance twice weekly during eight months in addition to usual school health services. Costs for the stakeholder of the intervention, treatment effect and healthcare costs were considered. Gained quality-adjusted life-years (QALYs) were used to measure the effects. Quality of life was measured with the Health Utility Index Mark 3. Cost-effectiveness ratios were based on the changes in QALYs and net costs for the intervention group compared with the control group. Likelihood of cost-effectiveness was calculated.

RESULTS

At 20 months, quality of life had increased by 0.08 units more in the intervention group than in the control group (P = .04), translating to 0.10 gained QALYs. The incremental cost-effectiveness ratio was USD $3,830 per QALY and the likelihood of cost-effectiveness was 95%.

CONCLUSIONS

Intervention with dance twice weekly in addition to usual school health services may be considered cost-effective compared with usual school health services alone, for adolescent girls with internalizing problems.

TRIAL REGISTRATION

Name of the trial registry: "Influencing Adolescent Girls' With Creative Dance Twice Weekly"

TRIAL REGISTRATION NUMBER

NCT01523561.

Asthma control cost-utility randomized trial evaluation (ACCURATE): the goals of asthma treatment

Background

Despite the availability of effective therapies, asthma remains a source of significant morbidity and use of health care resources. The central research question of the ACCURATE trial is whether maximal doses of (combination) therapy should be used for long periods in an attempt to achieve complete control of all features of asthma. An additional question is whether patients and society value the potential incremental benefit, if any, sufficiently to concur with such a treatment approach. We assessed patient preferences and cost-effectiveness of three treatment strategies aimed at achieving different levels of clinical control:

1. sufficiently controlled asthma

2. strictly controlled asthma

3. strictly controlled asthma based on exhaled nitric oxide as an additional disease marker

Design

720 Patients with mild to moderate persistent asthma from general practices with a practice nurse, age 18-50 yr, daily treatment with inhaled corticosteroids (more then 3 months usage of inhaled corticosteroids in the previous year), will be identified via patient registries of general practices in the Leiden, Nijmegen, and Amsterdam areas in The Netherlands. The design is a 12-month cluster-randomised parallel trial with 40 general practices in each of the three arms. The patients will visit the general practice at baseline, 3, 6, 9, and 12 months. At each planned and unplanned visit to the general practice treatment will be adjusted with support of an internet-based asthma monitoring system supervised by a central coordinating specialist nurse. Patient preferences and utilities will be assessed by questionnaire and interview. Data on asthma control, treatment step, adherence to treatment, utilities and costs will be obtained every 3 months and at each unplanned visit. Differences in societal costs (medication, other (health) care and productivity) will be compared to differences in the number of limited activity days and in quality adjusted life years (Dutch EQ5D, SF6D, e-TTO, VAS). This is the first study to assess patient preferences and cost-effectiveness of asthma treatment strategies driven by different target levels of asthma control.

Trial registration

Netherlands Trial Register (NTR): NTR1756

Sample size determination for cost-effectiveness trials

Methods for determining sample size requirements for cost-effectiveness studies are reviewed and illustrated. Traditional methods based on tests of hypothesis and power arguments are given for the incremental cost-effectiveness ratio and incremental net benefit (INB). In addition, a full Bayesian approach using decision theory to determine optimal sample size is given for INB. The full Bayesian approach, based on the value of information, is proposed in reaction to concerns that traditional methods rely on arbitrarily chosen error probabilities and an ill-defined notion of the smallest clinically important difference. Furthermore, the results of cost-effectiveness studies are used for decision making (e.g. should a new intervention be adopted or the old one retained), and employing decision theory, which permits optimal use of current information and the optimal design of new studies, provides a more consistent approach.

Implementing guidelines into clinical practice: what is the value?

RATIONALE AND OBJECTIVE

In budget-constrained health systems, decision makers need to consider both the costs and effects of introducing and actively implementing clinical guidance. We aim to demonstrate how, as an alternative to conventional methods, a total net benefit approach to economic evaluation can be used to inform decision making about guidelines and specific implementation strategies, like education or financial incentives.

METHODS

Aside from providing more detail on the decision framework, we describe how to collect and analyse the relevant data for calculating the total net benefit of guideline use and the value of implementation. We illustrate the process of decision analysis for a stylized example on improving diabetes care in the UK. For the analysis, economic evidence on intensified glycemic control and that on audit and feedback to promote control is combined with information on diabetes practice.

RESULTS

Our illustration demonstrates that the total net benefit of guideline use and the value of implementation can vary substantially, depending on the clinical intervention chosen, the health system being studied and the specific implementation strategies. This also holds for the threshold value for cost-effectiveness, the duration of guideline usage or validity, the size of the patient population served, and the trends and ceiling rates in the implementation of clinical guidance.

CONCLUSIONS

In comparison with conventional methods for health economic evaluation, a total net benefit approach allows for the explicit consideration of the current (or future) use of guidelines or guideline recommendations, the cost of implementation and the scope of clinical practice. Decisions made on the basis of the total net benefit of all plausible combinations of clinical guidance and implementation strategies provide optimal patient care and an efficient use of resources.

Sample size and power for cost-effectiveness analysis (part 1)

Basic sample size and power formulae for cost-effectiveness analysis have been established in the literature. These formulae are reviewed and the similarities and differences between sample size and power for cost-effectiveness analysis and for the analysis of other continuous variables such as changes in blood pressure or weight are described. The types of sample size and power tables that are commonly calculated for cost-effectiveness analysis are also described and the impact of varying the assumed parameter values on the resulting sample size and power estimates is discussed. Finally, the way in which the data for these calculations may be derived are discussed.

Value of information and value of implementation: application of an analytic framework to inform resource allocation decisions in metastatic hormone-refractory prostate cancer

OBJECTIVE

In a budget-constrained health-care system, decisions about investing in strategies to promote implementation have to be made alongside decisions about health-care provision and research funding. Using a Bayesian decision-theoretic approach, an analytic framework has been developed to inform these separate but related decisions, establishing the expected value of both perfect information (EVPI) and perfect implementation (EVPIM). We applied this framework to inform decision-making about resource allocation to metastatic hormone-refractory prostate cancer (mHRPC) in the UK.

METHODS

Based on available evidence on the cost-effectiveness of all plausible treatments for mHRPC, we determined which treatment option(s) were cost-effective and explored the uncertainty surrounding this decision. Given the decision uncertainty and the variation in care provided by health-care professionals, we then determined the EVPI and EVPIM. Finally, we performed sensitivity analyses to explore the influence of alternative assumptions regarding various decision parameters on the efficiency of resource allocation.

RESULTS

Depending on the cost-effectiveness threshold (lambda), we identified mitoxantrone plus prednisone/prednisolone and docetaxel plus prednisone/prednisolone (3 weekly) as the optimal treatments for mHRPC. Given current clinical practice, there appears to be considerable scope for improving the efficiency of health-care provision: the EVPI (estimated to be over pound13 million) indicates that acquiring further information could be cost-effective; and the EVPIM (estimated to be over pound4 million) suggests that investing in strategies to implement the treatments regimens being identified as optimal is potentially worthwhile. Through sensitivity analyses, we found that the EVPI and EVPIM are mainly driven by lambda, the number of treatment options being considered, the current level of implementation, and the size of the eligible patient population.

CONCLUSION

The application demonstrates that the framework provides a simple and useful analytic tool for decision-makers to address resource allocation problems between health-care provision, further research, and implementation efforts.

Globally optimal trial design for local decision making

Value of information methods allows decision makers to identify efficient trial design following a principle of maximizing the expected value to decision makers of information from potential trial designs relative to their expected cost. However, in health technology assessment (HTA) the restrictive assumption has been made that, prospectively, there is only expected value of sample information from research commissioned within jurisdiction. This paper extends the framework for optimal trial design and decision making within jurisdiction to allow for optimal trial design across jurisdictions. This is illustrated in identifying an optimal trial design for decision making across the US, the UK and Australia for early versus late external cephalic version for pregnant women presenting in the breech position. The expected net gain from locally optimal trial designs of US$0.72M is shown to increase to US$1.14M with a globally optimal trial design. In general, the proposed method of globally optimal trial design improves on optimal trial design within jurisdictions by: (i) reflecting the global value of non-rival information; (ii) allowing optimal allocation of trial sample across jurisdictions; (iii) avoiding market failure associated with free-rider effects, sub-optimal spreading of fixed costs and heterogeneity of trial information with multiple trials.

Joint distribution approaches to simultaneously quantifying benefit and risk

BACKGROUND

The benefit-risk ratio has been proposed to measure the tradeoff between benefits and risks of two therapies for a single binary measure of efficacy and a single adverse event. The ratio is calculated from the difference in risk and difference in benefit between therapies. Small sample sizes or expected differences in benefit or risk can lead to no solution or problematic solutions for confidence intervals.

METHODS

Alternatively, using the joint distribution of benefit and risk, confidence regions for the differences in risk and benefit can be constructed in the benefit-risk plane. The information in the joint distribution can be summarized by choosing regions of interest in this plane. Using Bayesian methodology provides a very flexible framework for summarizing information in the joint distribution.

RESULTS

Data from a National Institute of Child Health & Human Development trial of hydrocortisone illustrate the construction of confidence regions and regions of interest in the benefit-risk plane, where benefit is survival without supplemental oxygen at 36 weeks postmenstrual age, and risk is gastrointestinal perforation. For the subgroup of infants exposed to chorioamnionitis the confidence interval based on the benefit-risk ratio is wide (Benefit-risk ratio: 1.52; 90% confidence interval: 0.23 to 5.25). Choosing regions of appreciable risk and acceptable risk in the benefit-risk plane confirms the uncertainty seen in the wide confidence interval for the benefit-risk ratio--there is a greater than 50% chance of falling into the region of acceptable risk--while visually allowing the uncertainty in risk and benefit to be shown separately. Applying Bayesian methodology, an incremental net health benefit analysis shows there is a 72% chance of having a positive incremental net benefit if hydrocortisone is used in place of placebo if one is willing to incur at most one gastrointestinal perforation for each additional infant that survives without supplemental oxygen.

CONCLUSION

If the benefit-risk ratio is presented, the joint distribution of benefit and risk also should be shown. These regions avoid the ambiguity associated with collapsing benefit and risk to a single dimension. Bayesian methods allow even greater flexibility in simultaneously quantifying benefit and risk.

Nonparametric statistical methods for cost-effectiveness analyses

Two measures often used in a cost-effectiveness analysis are the incremental cost-effectiveness ratio (ICER) and the net health benefit (NHB). Inferences on these two quantities are often hindered by highly skewed cost data. In this article, we derive the Edgeworth expansions for the studentized t-statistics for the two measures and show how they could be used to guide inferences. In particular, we use the expansions to study the theoretical performance of existing confidence intervals based on normal theory and to derive new confidence intervals for the ICER and the NHB. We conduct a simulation study to compare our new intervals with several existing methods. The methods evaluated include Taylor's interval, Fieller's interval, the bootstrap percentile interval, and the bootstrap bias-corrected acceleration interval. We found that our new intervals give good coverage accuracy and are narrower compared to the current recommended intervals.

The value of information and optimal clinical trial design

Traditional sample size calculations for randomized clinical trials depend on somewhat arbitrarily chosen factors, such as type I and II errors. Type I error, the probability of rejecting the null hypothesis of no difference when it is true, is most often set to 0.05, regardless of the cost of such an error. In addition, the traditional use of 0.2 for the type II error means that the money and effort spent on the trial will be wasted 20 per cent of the time, even when the true treatment difference is equal to the smallest clinically important one and, again, will not reflect the cost of making such an error. An effectiveness trial (otherwise known as a pragmatic trial or management trial) is essentially an effort to inform decision-making, i.e. should treatment be adopted over standard? As such, a decision theoretic approach will lead to an optimal sample size determination. Using incremental net benefit and the theory of the expected value of information, and taking a societal perspective, it is shown how to determine the sample size that maximizes the difference between the cost of doing the trial and the value of the information gained from the results. The methods are illustrated using examples from oncology and obstetrics.

Cost-effectiveness analysis for multinational clinical trials

Clinical trials of cost-effectiveness are often conducted in more than one country. The two most common ways of dealing with the multinational nature of the data are either to calculate a pooled estimate or to stratify results by country. Since the between-country heterogeneity in costs is potentially substantial, pooled estimates may be difficult to interpret for any one country. Policy decisions are often made at a national level, and so country-specific results are important. However, country-specific analyses will be based on fewer patients and will often fail to provide adequate precision for statistical analyses. Shrinkage estimation is a compromise between these two methods and has been used successfully in other fields. These estimates are country-specific yet less variable than those derived through a subgroup approach. Univariate and multivariate shrinkage estimators for costs and effects are proposed, then compared with one another and to the traditional methods in a simulation study. The methods are illustrated using data from a multinational trial evaluating the cost-effectiveness of three thrombolytic drug regimens in patients with acute myocardial infarction.

Incremental net benefit in the analysis of economic data from clinical trials, with application to the CADET-Hp trial

In clinical trials it has become increasingly common for cost data to be collected in addition to data on clinical effectiveness. In response to this, new statistical methodology has been developed. Initially, efforts were focused on the incremental cost-effectiveness ratio, but as the problems with ratio statistics became apparent, attention was switched to incremental net benefit. In this paper statistical methods based on an incremental net benefit approach are given and illustrated with an example from the gastrointestinal literature. The relationship between incremental net benefit and incremental cost-effectiveness is emphasized.

Cost effectiveness analysis of a randomised trial of acupuncture for chronic headache in primary care

OBJECTIVE

To evaluate the cost effectiveness of acupuncture in the management of chronic headache.

DESIGN

Cost effectiveness analysis of a randomised controlled trial.

SETTING

General practices in England and Wales.

PARTICIPANTS

401 patients with chronic headache, predominantly migraine. Interventions Patients were randomly allocated to receive up to 12 acupuncture treatments over three months from appropriately trained physiotherapists, or to usual care alone.

MAIN OUTCOME MEASURE

Incremental cost per quality adjusted life year (QALY) gained.

RESULTS

Total costs during the one year period of the study were on average higher for the acupuncture group (403 pounds sterling; 768 dollars; 598 euros) than for controls (217 pounds sterling) because of the acupuncture practitioners' costs. The mean health gain from acupuncture during the one year of the trial was 0.021 quality adjusted life years (QALYs), leading to a base case estimate of 9180 pounds sterling per QALY gained. This result was robust to sensitivity analysis. Cost per QALY dropped substantially when the analysis incorporated likely QALY differences for the years after the trial.

CONCLUSIONS

Acupuncture for chronic headache improves health related quality of life at a small additional cost; it is relatively cost effective compared with a number of other interventions provided by the NHS.

Parametric modelling of cost data in medical studies

The cost of medical resources used is often recorded for each patient in clinical studies in order to inform decision-making. Although cost data are generally skewed to the right, interest is in making inferences about the population mean cost. Common methods for non-normal data, such as data transformation, assuming asymptotic normality of the sample mean or non-parametric bootstrapping, are not ideal. This paper describes possible parametric models for analysing cost data. Four example data sets are considered, which have different sample sizes and degrees of skewness. Normal, gamma, log-normal, and log-logistic distributions are fitted, together with three-parameter versions of the latter three distributions. Maximum likelihood estimates of the population mean are found; confidence intervals are derived by a parametric BC(a) bootstrap and checked by MCMC methods. Differences between model fits and inferences are explored.Skewed parametric distributions fit cost data better than the normal distribution, and should in principle be preferred for estimating the population mean cost. However for some data sets, we find that models that fit badly can give similar inferences to those that fit well. Conversely, particularly when sample sizes are not large, different parametric models that fit the data equally well can lead to substantially different inferences. We conclude that inferences are sensitive to choice of statistical model, which itself can remain uncertain unless there is enough data to model the tail of the distribution accurately. Investigating the sensitivity of conclusions to choice of model should thus be an essential component of analysing cost data in practice.

Regression methods for cost-effectiveness analysis with censored data

A system of seemingly unrelated regression equations is proposed for prognostic factor adjustment and subgroup analysis when comparing two groups in a cost-effectiveness analysis with censored data. Because of the induced dependent censoring on costs and quality-adjusted survival, inverse probability weighting is employed for parameter estimation. The method is illustrated with data from two recent examples using both survival time and quality-adjusted survival time as the measures of effectiveness.

Regression analysis of incomplete medical cost data

The accumulation of medical cost over time for each subject is an increasing stochastic process defined up to the instant of death. The stochastic structure of this process is complex. In most applications, the process can only be observed at a limited number of time points. Furthermore, the process is subject to right censoring so that it is unobservable after the censoring time. These special features of the medical cost data, especially the presence of death and censoring, pose major challenges in the construction of plausible statistical models and the development of the corresponding inference procedures. In this paper, we propose several classes of regression models which formulate the effects of possibly time-dependent covariates on the marginal mean of cost accumulation in the presence of death or on the conditional means of cost accumulation given specific survival patterns. We then develop estimating equations for these models by combining the approach of generalized estimating equations for longitudinal data with the inverse probability of censoring weighting technique. The resultant estimators are shown to be consistent and asymptotically normal with simple variance estimators. Simulation studies indicate that the proposed inference procedures behave well in practical situations. An application to data taken from a large cancer study reveals that the Medicare enrollees who are diagnosed with less aggressive ovarian cancer tend to accumulate medical cost at lower rates than those with more aggressive disease, but tend to have higher lifetime costs because they live longer.

Incremental net benefit in randomized clinical trials with quality-adjusted survival

Owing to induced dependent censoring, estimating mean costs and quality-adjusted survival in a cost-effectiveness comparison of two groups using standard life-table methods leads to biased results. In this paper we propose methods for estimating the difference in mean costs and the difference in mean effectiveness, together with their respective variances and covariance in the presence of dependent censoring. We consider the situation in which the measure of effectiveness is either the probability of surviving a duration of interest or mean quality-adjusted survival time over a duration of interest. The methods are illustrated in an example using an incremental net benefit analysis.

Advantages of using the net-benefit approach for analysing uncertainty in economic evaluation studies

No consensus has yet been reached on how to analyse uncertainty in economic evaluation studies where individual patient data are available for costs and health effects. This paper summarises the available results regarding the analysis of uncertainty on the cost-effectiveness plane and argues for using the net-benefit approach when analysing uncertainty in cost-effectiveness studies. The net-benefit approach avoids the interpretation and statistical problems related to the incremental cost effectiveness ratio and implies several advantages. First, traditional statistical methods can be used for confidence-interval estimation and hypothesis testing. Second, calculation of the optimal sample size and the power of the study are facilitated allowing the correlation between costs and effects to vary within and between patient groups. Third, the use of a Bayesian approach to cost-effectiveness analysis is facilitated. Fourth, a formal relation between cost-effectiveness acceptability curves and statistical inference is provided. Finally, the net-benefit approach gives the Fieller's limits of the confidence interval for the incremental cost-effectiveness ratio in the cost-effectiveness plane. Based on these advantages the net-benefit approach should strongly be considered when analysing uncertainty in cost-effectiveness analyses.

Using inverse-weighting in cost-effectiveness analysis with censored data

Due to induced dependent censoring, estimating mean costs and quality-adjusted survival in a cost-effectiveness analysis using standard life-table methods leads to biased results. In this paper we propose methods for estimating the difference in mean costs and the difference in effectiveness, together with their respective variances and covariance in the presence of dependent censoring. We consider the situation in which the measure of effectiveness is either the probability of patients surviving a duration of interest, mean survival time over a duration of interest or mean quality-adjusted survival time over a duration of interest. The method of inverse-weighting is used for censored cost and quality of life data. The methods are illustrated in an example using an incremental net benefit analysis.