Alastair Canaway’s journal round-up for 18th September 2017

Every Monday our authors provide a round-up of some of the most recently published peer reviewed articles from the field. We don’t cover everything, or even what’s most important – just a few papers that have interested the author. Visit our Resources page for links to more journals or follow the HealthEconBot. If you’d like to write one of our weekly journal round-ups, get in touch.

Selection of key health domains from PROMIS® for a generic preference-based scoring system. Quality of Life Research [PubMedPublished 19th August 2017

The US Panel on Cost-Effectiveness recommends the use of QALYs. It doesn’t, however, instruct (unlike the UK) as to what measure should be used. This leaves the door ajar for both new and established measures. This paper sets about developing a new preference-based measure from the Patient-Reported Outcomes Measurement System (PROMIS). PROMIS is a US National Institutes of Health funded suite of person-centred measures of physical, mental, and social health. Across all the PROMIS measures there exist over 70 domains of health relevant to adult health. For all its promise, the PROMIS system does not produce a summary score amenable to the calculation of QALYs, nor for general descriptive purposes such as measuring HRQL over time. This study aimed to reduce the 70 items down to a number suitable for valuation. To do this, Delphi methods were used. The Delphi approach is something that seems to be increasing in popularity in the health economics world. For those unfamiliar, it essentially involves obtaining the opinions of experts independently and iteratively conducting rounds of questioning to reach a consensus (over two or more rounds). In this case nine health outcomes experts were recruited, they were presented with ‘all 37 domains’ (no mention is made of how they got from 70 to 37!) and asked to remove any domains that were not appropriate for inclusion in a general health utility measure or were redundant due to another PROMIS domain. If more than seven experts agreed, then the domain was removed. Responses were combined and presented until consensus was reached. This left 10 domains. They then used a community sample of 50 participants to test for independence of domains using a pairwise independence evaluation test. They were given the option of removing a domain they felt was not important to overall HRQL and asked to rate the importance of remaining domains using a VAS. These findings were used by the research team to whittle down from nine domains to seven. The final domains were: Cognitive function- abilities; Depression; Fatigue; Pain Interference; Physical Function; Ability to participate in social roles and activities; and Sleep disturbance. Many of these are common to existing measures but I did rather like the inclusion of cognitive function and fatigue – something that is missing in many, and to me appear important. The next step is valuation. Upon valuation, this is a promising candidate for use in economic evaluation – particularly in the US where the PROMIS measurement suite is already established.

Predictive validation and the re-analysis of cost-effectiveness: do we dare to tread? PharmacoEconomics [PubMedPublished 22nd August 2017

PharmacoEconomics treated us to a provocative editorial regarding predictive validation and re-analysis of cost-effectiveness models – a call to arms of sorts. For those (like me) who are not modelling experts, predictive validation (aka 4th order validation) refers to the comparison of model outputs with data that are collected after the initial analysis of the model. So essentially you’re comparing what you modelled would happen with what actually happened. The literature suggests that predictive validation is widely ignored. The importance of predictive validity is highlighted with a case study where predictive-validity was examined three years after the end of a trial – upon reanalysis the model was poor. This was then revised, which led to a much better fit of the prospective data. Predictive validation can, therefore, be used to identify sources of inaccuracies in models. If predictive validity was examined more commonly, improvements in model quality more generally are possible. Furthermore, it might be possible to identify specific contexts where poor predictive validity is prevalent and thus require further research. The authors highlight the field of advanced cancers as a particularly relevant context where uncertainty around survival curves is prevalent. By actively scheduling further data collection and updating the survival curves we can reduce the uncertainty surrounding the value of high-cost drugs. Predictive validation can also inform other aspects of the modelling process, such as the best choice of time point from which to extrapolate, or credible rates of change in predicted hazards. The authors suggest using expected value of information analysis to identify technologies with the largest costs of uncertainty to prioritise where predictive validity could be assessed. NICE and other reimbursement bodies require continued data collection for ‘some’ new technologies, the processes are therefore in place for future studies to be designed and implemented in a way to capture such data which allows later re-analysis. Assessing predictive validity seems eminently sensible, there are however barriers. Money is the obvious issue, extended prospective data collection and re-analysis of models requires resources. It does, however, have the potential to save money and improve health in the long run. The authors note how in a recent study they demonstrated that a drug for osteoporosis that had been recommended by Australia’s Pharmaceutical Benefits Advisory Committee was not actually cost-effective when further data were examined. There is clearly value to be achieved in predictive validation and re-analysis – it’s hard to disagree with the authors and we should probably be campaigning for longer term follow-ups, re-analysis and increased acknowledgement of the desirability of predictive validity.

How should cost-of-illness studies be interpreted? The Lancet Psychiatry [PubMed] Published 7th September 2017

It’s a good question – cost of illness studies are commonplace, but are they useful from a health economics perspective? A comment piece in The Lancet Psychiatry examines this issue using the case study of self-harm and suicide. It focuses on a recent publication by Tsiachristas et al, which examines the hospital resource use and care costs for all presentations of self-harm in a UK hospital. Each episode of self-harm cost £809, and when extrapolated to the UK cost £162 million. Over 30% of these costs were psychological assessments which despite being recommended by NICE only 75% of self-harming patients received. If all self-harming patients received assessments as recommended by NICE then another £51 million would be added to the bill. The author raises the question of how much use is this information for health economists. Nearly all cost of illness studies end up concluding that i) they cost a lot, and ii) money could be saved by reducing or ameliorating the underlying factors that cause the illness. Is this helpful? Well, not particularly, by focusing only on one illness there is no consideration of the opportunity cost: if you spend money preventing one condition then that money will be displacing resources elsewhere, likewise, resources spent reducing one illness will likely be balanced by increased spending on another illness. The author highlights this with a thought experiment: “imagine a world where a cost of illness study has been done for every possible diseases and that the total cost of illness was aggregated. The counterfactual from such an exercise is a world where nobody gets sick and everybody dies suddenly at some pre-determined age”. Another issue is that more often than not, cost of illness studies identify that more, not less should be spent on a problem, in the self-harm example it was that an extra £51 million should be spent on psychological assessments. Similarly, it highlights the extra cost of psychological assessments, rather than the glaring issue that 25% who attend hospital for self-harm are not getting the required psychological assessments. This very much links into the final point that cost of illness studies neglect the benefits being achieved. Now all the negatives are out the way, there are at least a couple of positives I can think of off the top of my head i) identification of key cost drivers, and ii) information for use in economic models. The take home message is that although there is some use to cost of illness studies, from a health economics perspective we (as a field) would be better off spending our time steering clear.

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