Missing data in trial-based cost-effectiveness analysis: An incomplete journey

Cost-effectiveness analyses (CEA) conducted alongside randomised trials provide key evidence for informing healthcare decision making, but missing data pose substantive challenges. Recently, there have been a number of developments in methods and guidelines addressing missing data in trials. However, it is unclear whether these developments have permeated CEA practice. This paper critically reviews the extent of and methods used to address missing data in recently published trial-based CEA. Issues of the Health Technology Assessment journal from 2013 to 2015 were searched. Fifty-two eligible studies were identified. Missing data were very common; the median proportion of trial participants with complete cost-effectiveness data was 63% (interquartile range: 47%-81%). The most common approach for the primary analysis was to restrict analysis to those with complete data (43%), followed by multiple imputation (30%). Half of the studies conducted some sort of sensitivity analyses, but only 2 (4%) considered possible departures from the missing-at-random assumption. Further improvements are needed to address missing data in cost-effectiveness analyses conducted alongside randomised trials. These should focus on limiting the extent of missing data, choosing an appropriate method for the primary analysis that is valid under contextually plausible assumptions, and conducting sensitivity analyses to departures from the missing-at-random assumption

A brief intervention for weight control based on habit-formation theory delivered through primary care: results from a randomised controlled trial

Background: Primary care is the 'first port of call' for weight control advice, creating a need for simple, effective interventions that can be delivered without specialist skills. Ten Top Tips (10TT) is a leaflet based on habit-formation theory that could fill this gap. The aim of the current study was to test the hypothesis that 10TT can achieve significantly greater weight loss over 3 months than ‘usual care’. Methods: A two-arm, individually randomised, controlled trial in primary care. Adults with obesity were identified from 14 primary care providers across England. Patients were randomised to either 10TT or 'usual care' and followed up at 3, 6, 12, 18 and 24 months. The primary outcome was weight loss at 3 months, assessed by a health professional blinded to group allocation. Difference between arms was assessed using a mixed-effect linear model taking into account the health professionals delivering 10TT, and adjusted for baseline weight. Secondary outcomes included body mass index, waist circumference, the number achieving a 5% weight reduction, clinical markers for potential comorbidities, weight loss over 24 months and basic costs. Results: Five-hundred and thirty-seven participants were randomised to 10TT (n=267) or to ‘usual care' (n=270). Data were available for 389 (72%) participants at 3 months and for 312 (58%) at 24 months. Participants receiving 10TT lost significantly more weight over 3 months than those receiving usual care (mean difference =−0.87kg; 95% confidence interval: −1.47 to −0.27; P=0.004). At 24 months, the 10TT group had maintained their weight loss, but the ‘usual care’ group had lost a similar amount. The basic cost of 10TT was low, that is, around £23 ($32) per participant. Conclusions: The 10TT leaflet delivered through primary care is effective in the short-term and a low-cost option over the longer term. It is the first habit-based intervention to be used in a health service setting and offers a low-intensity alternative to ‘usual care’

From Scattering Amplitudes to the Dilatation Generator in N=4 SYM

The complete spin chain representation of the planar N=4 SYM dilatation generator has long been known at one loop, where it involves leading nearest-neighbor 2 -> 2 interactions. In this work we use superconformal symmetry to derive the unique solution for the leading L -> 2 interactions of the planar dilatation generator for arbitrarily large L. We then propose that these interactions are given by the scattering operator that has N=4 SYM tree-level scattering amplitudes as matrix elements. We provide compelling evidence for this proposal, including explicit checks for L=2,3 and a proof of consistency with superconformal symmetry.Comment: 39 pages, v2: reference added and minor changes, published versio

Cost-effectiveness analysis with informative missing data: tools and strategies

Cost effectiveness analysis (CEA) of randomised trials are an important source of evidence for informing policy makers on how to best allocate limited resources. Missing data are a common issue in trial-based CEA, and methods such as multiple imputation are now commonly used to account for the missing values, assuming the data are ‘missing at random’ (MAR). This implies that the reasons for the missing data can be explained by the observed data. However, the missingness is often related to unobserved values, that is data are ‘missing not at random’ (MNAR, or ‘informative’). For example, patients whose health status is relatively poor may be less likely to return health questionnaires, even conditional on their observed characteristics. In these settings, methodological guidance recommends assessing whether conclusions are sensitive to departures from the MAR assumption. Sensitivity analysis strategies for handling MNAR is an area of rapid development in medical statistics, but this form of uncertainty has not yet been appropriately addressed in health economics. This PhD thesis aims to develop practical, accessible sensitivity analysis strategies and software tools to handle MNAR data in trial-based CEA. The thesis critically assessed the statistical methods for handling MNAR data in CEA practice, and identified barriers to more widespread use of these methods, via a systematic review and stakeholder focus groups. The research then focused on two strategies to conduct sensitivity analysis under MNAR assumptions: pattern-mixture models, which involve imputing the data assuming MAR, then modifying the imputed values to reflect possible departures from that assumption; and reference-based imputation, where the data are imputed assuming a distribution borrowed from a ‘reference group’. These approaches were illustrated in CEAs of 10TT and CoBalT trials, which evaluated weight loss and depression interventions. Software code and practical guidance are provided to facilitate implementation in practice

Is positive school climate and adolescent mental health: Longitudinal study of young people in England

Background and objectives: Studies suggest that individual student-reported connection to school is associated with better mental health. However, there is less evidence for associations between schools’ overall school climate and the mental health of their students. This may reflect limitations in which mental health outcomes have been examined. We conducted a large longitudinal study in schools, hypothesising that we would find associations at both the student and school levels between student-reported positive school climate, and reduced student conduct and emotional problems and improved mental wellbeing. // Methods: We tracked students in 20 English secondary schools from near the end of the first year of secondary school (age 11/12) over 3 years using reliable measures of school climate and mental health. // Results: We found associations between student-level reports of positive school climate at baseline, and reduced conduct and emotional problems and better mental wellbeing at 3-year follow-up adjusting for various potential confounders. We also found some evidence of adjusted associations between baseline school-level measures of overall positive climate and better student mental health at follow-up. However, these student- and school-level associations reduced considerably when also adjusting for baseline mental health. // Conclusions: Our findings suggest that there are associations between school climate and student mental health at both the student and school level but these associations are complex and not necessarily causal

Sensitivity Analysis for Not-at-Random Missing Data in Trial-Based Cost-Effectiveness Analysis : A Tutorial

Cost-effectiveness analyses (CEA) of randomised controlled trials are a key source of information for health care decision makers. Missing data are, however, a common issue that can seriously undermine their validity. A major concern is that the chance of data being missing may be directly linked to the unobserved value itself [missing not at random (MNAR)]. For example, patients with poorer health may be less likely to complete quality-of-life questionnaires. However, the extent to which this occurs cannot be ascertained from the data at hand. Guidelines recommend conducting sensitivity analyses to assess the robustness of conclusions to plausible MNAR assumptions, but this is rarely done in practice, possibly because of a lack of practical guidance. This tutorial aims to address this by presenting an accessible framework and practical guidance for conducting sensitivity analysis for MNAR data in trial-based CEA. We review some of the methods for conducting sensitivity analysis, but focus on one particularly accessible approach, where the data are multiply-imputed and then modified to reflect plausible MNAR scenarios. We illustrate the implementation of this approach on a weight-loss trial, providing the software code. We then explore further issues around its use in practice

Brief intervention for alcohol misuse in people attending sexual health clinics: study protocol for a randomized controlled trial.

BACKGROUND: Over the last 30  years the number of people who drink alcohol at harmful levels has increased in many countries. There have also been large increases in rates of sexually transmitted infections. Available evidence suggests that excessive alcohol consumption and poor sexual health may be linked. The prevalence of harmful alcohol use is higher among people attending sexual health clinics than in the general population, and a third of those attending clinics state that alcohol use affects whether they have unprotected sex. Previous research has demonstrated that brief intervention for alcohol misuse in other medical settings can lead to behavioral change, but the clinical- and cost-effectiveness of this intervention on sexual behavior have not been examined. METHODS: We will conduct a two parallel-arm, randomized trial. A consecutive sample of people attending three sexual health clinics in London and willing to participate in the study will be screened for excessive alcohol consumption. Participants identified as drinking excessively will then be allocated to either active treatment (Brief Advice and referral for Brief Intervention) or control treatment (a leaflet on healthy living). Randomization will be via an independent and remote telephone randomization service and will be stratified by study clinic. Brief Advice will comprise feedback on the possible health consequences of excessive alcohol consumption, written information about alcohol and the offer of an appointment for further assessment and Brief Intervention. Follow-up data on alcohol use, sexual behavior, health related quality of life and service use will be collected by a researcher masked to allocation status six months later. The primary outcome for the study is mean weekly alcohol consumption during the previous three months, and the main secondary outcome is the proportion of participants who report unprotected sex during this period. DISCUSSION: Opportunistic intervention for excessive alcohol use has been shown to be effective in a range of medical settings. The SHEAR study will examine whether delivering such interventions in sexual health clinics results in reductions in alcohol consumption and will explore whether this is associated with changes in sexual behavior

Cost-effectiveness of habit-based advice for weight control versus usual care in general practice in the Ten Top Tips (10TT) trial: economic evaluation based on a randomised controlled trial

Objective: Ten Top Tips (10TT) is a primary care-led behavioural intervention which aims to help adults reduce and manage their weight by following 10 weight loss tips. The intervention promotes habit formation to encourage long-term behavioural changes. The aim of this study was to estimate the cost-effectiveness of 10TT in general practice from the perspective of the UK National Health Service. Design: An economic evaluation was conducted alongside an individually randomised controlled trial. Setting: 14 general practitioner practices in England. Participants: All patients were aged ≥18 years, with body mass index ≥30 kg/m2. A total of 537 patients were recruited; 270 received the usual care offered by their practices and 267 received the 10TT intervention. Outcomes measures: Health service use and quality-adjusted life years (QALYs) were measured over 2 years. Analysis was conducted in terms of incremental net monetary benefits (NMBs), using non-parametric bootstrapping and multiple imputation. Results: Over a 2-year time horizon, the mean costs and QALYs per patient in the 10TT group were £1889 (95% CI £1522 to £2566) and 1.51 (95% CI 1.44 to 1.58). The mean costs and QALYs for usual care were £1925 (95% CI £1599 to £2251) and 1.51 (95% CI 1.45 to 1.57), respectively. This generated a mean cost difference of −£36 (95% CI −£512 to £441) and a mean QALY difference of 0.001 (95% CI −0.080 to 0.082). The incremental NMB for 10TT versus usual care was £49 (95% CI −£1709 to £1800) at a maximum willingness to pay for a QALY of £20 000. 10TT had a 52% probability of being cost-effective at this threshold. Conclusions: Costs and QALYs for 10TT were not significantly different from usual care and therefore 10TT is as cost-effective as usual care. There was no evidence to recommend nor advice against offering 10TT to obese patients in general practices based on cost-effectiveness considerations

Correction to: Sensitivity Analysis for Not-at-Random Missing Data in Trial-Based Cost-Effectiveness Analysis: A Tutorial

The original article can be found online at https://doi.org/10.1007/s40273-018-0650-5

The management of behavioural and psychological symptoms of dementia in the acute general medical hospital: a longitudinal cohort study.

BACKGROUND: The acute hospital is a challenging place for a person with dementia. Behavioural and psychological symptoms of dementia (BPSD) are common and may be exacerbated by the hospital environment. Concerns have been raised about how BPSD are managed in this setting and about over reliance on neuroleptic medication. This study aimed to investigate how BPSD are managed in UK acute hospitals. METHOD(S): A longitudinal cohort of 230 patients with dementia admitted to two acute NHS hospitals. BPSD were measured every four days (Behave-AD scale), as well as documentation of pharmacological prescriptions and non-pharmacological management. RESULTS: The overall prevalence of BPSD was 75%, with aggression and activity disturbance being the most common. Antipsychotics were prescribed for 28 (12%) patients; 70% of these prescriptions were new on admission. Benzodiazepines were prescribed for 27 (12%) patients, antidepressants were prescribed for 37 (16%) patients, and sedatives were prescribed for 14 (3%) patients. Patients who were prescribed antipsychotics, after adjusting for end of life medication, age and dementia severity, were significantly more likely to die (adjusted hazard ratio 5.78, 95% CI 1.57, 21.26, p = 0.008). Non-pharmacological management was used in 55% of participants, most commonly psychosocial interventions (36%) with little evidence of monitoring their effectiveness. A form of restraint was used during 50 (22%) patients' admissions. CONCLUSIONS: Antipsychotic medications and psychosocial interventions were the main methods used to manage BPSD; however, these were not implemented or monitored in a systematic fashion